GIFT  OF 
Agriculture  education 


GENERAL  SCIENCE 

AND  THE 
ECONOMICS  OF  DAILY  LIFE 


BROWNELL 


A  TEXTBOOK  IN 

GENERAL  SCIENCE 

AND  THE 
ECONOMICS  OF   DAILY  LIFE 


BY 

HERBERT  BROWNELL,  B.  Sc. 

PROFESSOR  OF  SCIENCES  IN  SECONDARY  EDUCATION,  TEACHERS  COLLEGE, 

UNIVERSITY  OF  NEBRASKA,  LINCOLN;  AUTHOR  OF  "LESSONS  IN 

PHYSICS",  "LESSONS  IN  CHEMISTRY",  AND  "LABORATORY 

LESSONS  IN  GENERAL  SCIENCE" 


WITH  118  ILLUSTRATIONS 


PHILADELPHIA 

P.  BLAKISTON'S  SON  &  CO. 

1012  WALNUT  STREET 


COPYRIGHT,  1918,  BY  P.  BLAKISTON'S  SON  &  Co. 
/  (   £  r 

ry; 


THK     MAPI,  K      I  •  K   K  s   S     YORK     PA 


PREFACE 


A  science,  as  the  term  is  usually  employed,  implies  a  group- 
ing of  the  facts  and  phenomena  of  some  one  field  of  human 
knowledge  according  to  certain  general  statements  known 
as  theories  and  laws.  Botany,  for  instance,  is  a  classification 
of  man's  knowledge  of  plants,  and  of  the  conditions  for  their 
growth.  It  makes  possible  the  study  of  plants  in  groups  rather 
than  one  by  one. 

But  in  General  Science  as  a  high  school  subject  selections  of 
topics  for  study  are  made  from  any  and  all  of  the  secondary 
school  sciences.  These  topics  are  studied  for  the  general 
purpose  of  giving  scientific  explanations  to  whatever  affects 
daily  life  in  so  far  as  they  lend  themselves  readily  to  elemen- 
tary scientific  discussions.  Some  theory  is  given  as  needed 
in  these  explanations,  but  there  is  little  or  no  regard  to 
whether  the  facts  and  explanations  have  to  do  with  any  one 
science  or  another.  Sufficient  experimental  phenomena  are 
to  be  provided  in  laboratory  exercises  and  classroom  demon- 
strations. The  topics  are  supposed  to  be  more  or  less  familiar 
through  the  common  experiences  of  childhood  and  youth, 
and  of  such  a  nature  as  to  foster  a  scientific  spirit. 

This  text  seeks  to  relate  for  schoolroom  uses  the  teachings 
of  science  and  the  common  experiences  of  life.  Its  dis- 
cussions are  designed  to  stimulate  a  desire  on  the  part  of 
pupils  for  information  concerning  everyday  phenomena 
readily  obtainable  from  high  school  science  texts,  and  from 
reference  books  suited  for  use  in  elementary  science  teaching. 

Some  of  the  discussions  of  the  text  though  elementary  in 
character  will  present  difficulties  for  beginners.  But  the 

v 

387901 


vi  PREFACE 

author  believes  it  advantageous  early  in  the  course  to  make 
some  use  of  the  theories  of  high  school  science  in  order  to 
give  scientific  unity  to  explanations  of  various  common 
phenomena.  Care  has  been  exercised  to  distinguish  sharply 
at  all  times  between  fact  and  theory,  and  to  make  clear  the 
restrictions  that  must  accompany  the  use  of  theories  whether 
in  school  or  elsewhere. 

Enough  of  a  knowledge  of  the  differentiated  high  school 
sciences  should  be  gained  in  a  general  science  course  to  serve 
as  a  real  introduction  to  them.  This  will  enable  pupils 
later  to  make  an  intelligent  choice  of  which  of  these  sciences 
they  care  to  pursue. 

However  skillfully  information  for  beginners  in  science 
may  be  selected  and  presented,  it  will  fail  very  largely  of  its 
purposes  as  " knowledge-making  material"  if  no  need  for  it 
has  arisen  in  the  minds  of  pupils,  and  if  no  apparent  use  for 
it  exists.  Where  a  desire  for  knowledge  is  based  on  needs 
that  have  been  experienced,  it  calls  forth  effort  in  the  school- 
room even  as  it  does  in  the  larger  field  of  life  experiences. 
A  purpose  of  the  text  is  to  arouse  and  in  some  large  measure 
to  guide  the  desires  of  pupils  for  a  scientific  understanding  of 
life's  problems,  and  to  furnish  some  of  the  material  and  con- 
ditions necessary  to  secure  these  ends. 

Perhaps  foremost  of  all  the  ends  sought  in  the  teachings 
of  General  Science  is  an  habitual  scientific  attitude  of  the 
pupils — the  state  of  mind  that  demands  the  facts  in  all 
cases;  that  discriminates  in  the  relative  importance  and 
pertinence  of  facts;  that  can  so  associate  them  as  to  get  their 
chief  significance  whether  in  specific  relationships  or  in  gen- 
eral applications;  that  does  not  rest  satisfied  with  "glittering 
generalities"  but  tests  them  out  to  ascertain  if  theory  fits 
facts  when  applied  to  known  conditions  and  existing  situa- 
tions. In  other  words,  the  facts  of  the  discussions  in  General 
Science,  valuable  as  they  may  be  in  themselves,  are  to  be 


PREFACE  Vll 

used  for  the  larger  purpose  of  establishing  a  scientific  pro- 
cedure in  the  affairs  of  life. 

The  author  desires  to  express  his  deep  appreciation  of  the 
helpful  suggestions  and  criticisms  of  those  who  have  read 
the  manuscript  for  this  text,  or  portions  of  it.  Special 
acknowledgments  are  due  Dr.  R.  J.  Pool  of  the  Department 
of  Botany;  Professor  H.  C.  Filley  of  the  Department  of 
Farm  Management;  Professor  Alice  M.  Loomis  of  the 
Department  of  Home  Economics;  Professor  George  E.  Love- 
land,  Director  of  the  U.  S.  Weather  Bureau;  Professor  G.  D. 
Swezey  of  the  Department  of  Astronomy;  and  Dr.  R.  A. 
Lyman  of  the  Department  of  Physiology,  all  of  the  Univer- 
sity of  Nebraska,  together  with  Professor  B.C.  Hendricks  of 
the  Department  of  Physics  in  the  State  Normal  School  at 
Peru,  Nebraska.  He  is  under  special  obligation  to  Professor 
A.  E.  Sheldon,  Lecturer  on  Political  History  and  Secretary 
of  the  State  Historical  Society,  and  to  Mrs.  Sheldon,  for 
their  very  helpful  criticisms  in  their  readings  of  the  manu- 
script. The  author  assumes,  however,  all  responsibility 
for  errors  that  may  have  crept  into  the  text. 

Aside  from  acknowledgments  made  in  connection  with 
single  illustrations,  the  author  wishes  to  express  his  apprecia- 
tion for  other  illustrations  from  : 

U.  S.  Forest  Service,— Figs.  37    40,  76,  83,  84,  86,  88. 

U.  S.  Weather  Bureau, — Figs.  32,  48,  102. 

U.  S.  Public  Health  Service,— Figs.  15,  21,  25. 

U.  S.  Public  Roads  and  Engineering, — Figs.  29,  69. 

U.  S.  Reclamation  Service, — Figs.  38,  39. 

U.  S.  Geological  Survey, — Figs.  92,  112. 

Division  of  Publications,  U.  S.  Department  of  Agriculture, — 
18,  24,  26,  27  28,  36,  47,  67  68,  73,  75,  77,  79,  80,  81,  82,  85,  93, 
95>  96,  97,  98,  103,  104,  105,  106,  107,  108,  in. 


CONTENTS 


PAGE 
I.  SOME  LESSONS  ON  THE  HUMAN  BODY. 

The  Hand 2 

The  Mouth 4 

The  Eye 10 

II.  HEAT  IN  RELATION  TO  THE  HUMAN  BODY. 

Combustion 16 

Pure  Air,  and  Breathing 19 

The  Human  Body  as  an  Engine,  and  the  Regulation  of  Body 

Temperature 25 

III.  HEALTH  AND  WELL-BEING. 

Keeping  Well 31 

Infection 36 

Sanitation 45 

The  Water  Supply  and  Health 52 

General  Health  Problems 57 

Life,  Growth,  Rest,  and  Recreation 64 

Stimulants  and  Narcotics 72 

General  Science  and  Right  Living 80 

IV.  WATER  AND  ITS  USES. 

Some  Properties  of  Water 85 

Vaporization  and  Condensation 90 

Heat  of  Vaporization  and  of  Fusion 94 

Solution,  Diffusion,  Absorption,  and  Osmosis 97 

Streams,  Valley  Formation,  and  Surface  Erosion 102 

V.  THE  ATMOSPHERE. 

Properties  and  Uses  of  Air no 

Pressure  Exerted  by  the  Atmosphere,  and  Effect  of  Pressure  on 

Gases 114 

Applications  of  Atmospheric  Pressure 118 

Currents  in  the  Atmosphere,  and  Their  Relation  to  Atmospheric 

Pressure 123 

Areas  of  High  and  Low  Pressure 128 

ix 


X  CONTENTS 

PAGE 
VI.  WEATHER  AND  CLIMATE. 

Weather  in  the  Affairs  of  Men 133 

Weather  as  Affected  by  Highs  and  Lows 137 

The  Thermometer,  and  Heat  Transmission 140 

Solar  Heating 147 

-,yil.  MATTER  AND  FORCE. 

Some  Properties  of  Matter,  and  Changes  in  Matter  Due  to  Force  151 

VIII.  WORK  AND  MACHINES. 

Meaning  of  the  Terms  Work  and  Energy 160 

*Levers  and  Pulleys 163 

Electromagnets 168 

IX.  SOME  CHEMISTRY  OF  EVERYDAY  LIFE. 

A  Review  of  Some  Chemical  Changes 173 

*The  Chemistry  of  Cleaning • .  • 177 

*Acids,  Bases,  and  Salts A  .    .  180 

*Electricity  and  Chemical  Changes 184 

"Limestone  and  Other  Carbonates 190 

*The  Chief  Among  Metals 196 

X.  AT  OUR  HOMES. 

Rooms  of  the  House,  Their  Furnishings,  and  the  Cost  of  Living  206 

Fuel  and  Lights  for  Modern  Homes • 214 

Some  Foodstuffs 219 

*  The  Carbohydrates .    .  226 

Fires,  Burns,  and  Various  Accidents 233 

XI.  SURROUNDINGS  OF  THE  HOME. 

The  Garden,  and  Its  Care    .    . .    .    .  241 

Soil  Conditions  for  Plant  Growth 247 

Tree  Planting *-'.    .    .    .  254 

Trees  of  the  Neighborhood 259 

Some  Plant  Studies 263 

Usefulness  of  Plants  to  Man 268 

Birds  Around  Our  Homes 275 

XII.  SOME  CONDITIONS  AFFECTING  INDUSTRIAL  LIFE. 

Changes  in  Manner  of  Living 281 

Social  and  Economic  Conditions  Affecting  the  Wage  Earner .    .  290 

*See  page  372. 


CONTENTS  xi 

PAGE 

XIII.  THE  FARM. 

Poultry  and  Eggs 297 

The  Horse 304 

Cows,  and  the  Dairy  Industry 307 

Lessons  on  Corn 312 

Apple  Raising  as  an  Industry 319 

Wheat,  and  Wheat  Growing    . 325 

Origin  and  Nature  of  Soils 332 

XIV.  PHENOMENA  OF  LIGHT. 

Shadows  and  Eclipses 336 

*Images  by  Reflection  in  Plane  Mirrors 338 

*Color  Phenomena , 342 

XV.  THE  EARTH  AS  A  PLANET. 

Day  and  Night,  and  the  Earth's  Rotation 349 

Rotation  Combined  With  Revolution,  and  Changes  in  Seasons  351 

The  Moon,  and  Its  Phenomena 355 

Time,  and  Time-keeping,  and  Standard  Time    .    .    .    .    .    .    .359 

XVI.  THE  HEAVENS 364 

APPENDIX. 

Suggestions  to  Teachers 370 

Reference  Books 372 

*  See  page  372. 


GENERAL  SCIENCE 


I.  SOME  LESSONS  ON  THE  HUMAN  BODY1 

INTRODUCTION 

We  expect  a  surgeon  to  have  an  intimate  knowledge  of 
human  anatomy,  and  a  physician  to  be  skilled  in  human 
physiology.  But  enough  of  the  anatomy  and  physiology 
of  the  human  body  should  be  taught  in  schools  so  that  in- 
struction in  hygiene  as  a  study  of  health  conditions  will  be 
better  understood  by  every  one,  and  its  teachings  better 
observed.  The  importance  of  an  understanding  of  health 
conditions,  and  of  their  control,  is  emphasized  in  the  lessons 
that  follow,  as  are  the  relations  between  good  health  and 
the  happiness  of  mankind.  The  lessons  on  the  Hand, 
Mouth,  and  Eye  are  given  because  of  the  peculiar  usefulness 
to  man  of  these  important  organs  of  his  body.  No  one 
should  be  ignorant  of  their  structure  and  uses  and  care.  A 
large  part  of  the  knowledge  of  the  world  around  us  is  gained 
through  the  eyes  and  hands,  and  life's  activities  are  largely 
dependent  upon  their  services.  Then,  too,  the  progress  of 
man  in  civilization  and  much  of  his  enjoyment  is  intimately 
associated  with  oral  speech  in  which  the  structure  of  the 

1  In  Zoology  as  a  study  of  all  forms  of  animals,  including  human  beings, 
anatomy  deals  largely  with  the  structure  of  the  body,  while  physiology  has  to 
do  with  the  activities  of  the  various  organs.  Botany  as  a  study  of  plants 
likewise  has  its  subdivisions  of  anatomy  and  physiology.  Biology  is  the 
science  of  living  bodies,  and  includes  both  Botany  and  Zoology. 

I 


2  GENERAL  SCIENCE 

. 

mouth  plays  a  most  important  part.  Some  knowledge  of 
Human  Physiology  as  studied  in  schools  is  presupposed  in 
these  lessons. 

THE  HAND 

The  bones  of  the  hand  serve  as  a  framework,  giving  to  it 
both  form  and  strength.  The  many  joints  of  the  hand  and 

wrist  make  possible  a  great 
variety  of  movements,  and  a 
wide  adaptability  in  uses. 
The  bones  are  held  together 
at  the  joints  by  ligaments, 
and  the  surfaces  of  bones 
that  move  upon  each  other 
are  covered  by  cartilage.  A 
study  of  both  cartilage  and 
ligaments  can  be  made  from 
a  joint  obtained  at  a  meat  shop. 
Motion  in  the  parts  of  the 
hand  and  wrist  is  accomplished 
by  means  of  muscles,  the  "lean 
meat"  of  animals.  Sometimes 
the  muscles  are  attached  directly 
to  the  bones,  seeming  to  grow 
out  of  the  bone  itself.  In  the 

wrist  and  hand  the  movement  of  cord-like  tendons  beneath 
the  skin  may  be  seen  and  felt.  The  muscles  here  are  at 
some  distance  from  the  bones  moved  by  them,  and  are 
connected  to  the  bones  by  the  tendons. 

To  cause  these  muscles  to  act,  moving  the  hand  and  fingers 
or  holding  them  at  rest  as  a  person  desires,  the  muscles  are 
provided  with  nerves.  In  the  skin  of  the  inner  part  of  the 
hand  and  fingers  the  terminal  fibres  of  the  nerves  are  so 
close  that  the  hand  through  care  and  training  may  acquire  a 


FIG.  i. — Bones  of  the  right  fore- 
arm, a,  palm;  b,  back  of  hand;  r,r', 
radius;  u,  uf,  ulna. 


SOME  LESSONS  ON  THE  HUMAN  BODY  3 

marvelous  delicacy  of  touch.  The  blind  learn  to  read 
through  their  finger  tips,  and  players  of  the  violin  and  other 
musical  instruments  seem  almost  to  think  with  their  fingers, 
so  intimate  is  the  relation  of  muscle  and  mind  through  the 
nerves. 

The  hair,  finger  nails,  and  outer  layers  of  the  skin  are 
all  destitute  of  blood  vessels.  Growth  in  them  occurs  only 
at  their  under  surfaces  and  inner  ends.  The  tendons  and 
ligaments,  too,  get  a  scant  supply  of  blood,  and  their  repair 
is  slow  after  accidents  where  a  sprain  has  occurred,  or  when 
they  have  been  torn  from  the  bone.  Either  condition  may 
be  more  serious  than  a  broken  bone,  or  the  dislocation  of 
bones  at  a  joint. 

The  finger  nails  serve  to  support  and  protect  the  ends  of 
the  fingers,  and  to  enable  a  person  to  pick  up  small  objects 
more  readily.  At  all  times  they  should  be  kept  neatly 
trimmed,  and  scrupulously  clean.  The  fold  of  skin  at  the 
base  of  the  nail  should  be  kept  pushed  back  instead  of  being 
cut  off.  Food  should  never  be  handled  with  unwashed 
hands,  nor  the  finger  tips  touched  to  the  tongue. 

The  hand  is  man's  chief  instrument  for  labor.  He  uses 
it  for  feeding  and  dressing  himself.  It  is  a  weapon  for  self- 
defense,  and  is  a  means  for  fashioning  tools,  implements, 
clothing,  and  for  preparing  his  food.  It  is  in  almost  constant 
use  during  man's  waking  hours,  ministering  to  his  needs  and 
executing  his  desires. 

SUMMARY 

In  shapeliness,  structure,  and  adaptability  the  hand  is  a  wonderful 
tool  fashioned  for  man's  use.  In  its  varied  movements  is  illustrated 
the  fact  that  the  muscles  are  the  organs  of  motion  in  the  body.  These 
muscles  move  in  obedience  to  impulses  sent  outward  to  them  from 
nerve  centers,  the  chief  of  which  is  the  brain. 

The  ability  of  man  to  labor  and  to  care  for  himself  is  seriously  im- 
paired when  he  is  deprived  of  his  hands.  His  mind,  too,  is  robbed  of 


GENERAL  SCIENCE 


t  — 


the  stimulus  of  directing  those  activities  in  which  the  hands  are  em- 
ployed, and  of  those  reactions  which  result  from  expression  of  thought 
through  hand  work. 

THE  MOUTH 

The  cavity  known  as  the  mouth  is  not  only  the  beginning 
of  the  digestive  canal,  but  it  is  one  of  the  chief  organs  of 
speech.  In  Physics  from  the  study  ^of 
sound  we  learn  something  of  the  uses  of 
the  mouth  and  its  adjacent  parts  in  talk- 
ing and  in  singing.  Complete  control  of 
the  muscular  parts  of  the  mouth  and  its 
connected  cavities  is  necessary  to  a  singer 
in  order  to  give  utterance  to  sounds  in  their 
proper  relationship  in  the  musical  scale. 

Just  above  the  larynx,  and  embedded 
in  the  tissues,  there  may  be  felt  on  either 
side  of  the  neck  the  small  semi-elliptical 
hyoid  bone.  From  it  many  of  the  mus- 
cular fibres  of  the  tongue  arise.  It  does 
not  connect  with  other  bones  of  the 

<•     ,1        i  •      T     • 

skeleton — the  only  case  of    the  kind  in 

^Q    body.       As    a    movable    bdS6    it    gives 

to  the  tongue  an  exceedingly  wide  range 
of  movement.  Back  of  the  mouth  cavity  and  the  at- 
tached end  of  the  'tongue  is  another  cavity  with  muscular 
walls  known  as  the  pharynx  (far'-inks).  This  is  the  upper 
enlarged  extremity  of  the  muscular  food  tube,  or  oesophagus, 
which  leads  to  the  stomach.  Food  and  drink,  when  forced 
by  the  tongue  back  into  the  pharynx,  pass  over  the  glottis, 
or  entrance  to  the  larynx,  and  are  kept  from  getting  into 
it  by  a  cartilaginous  cover  known  as  the  epiglottis.  Cough- 
ing, strangling,  and  choking  mark  spasmodic  efforts  to  dis- 
lodge food  or  drink  that  gets  into  the  glottis.  Once  within 


FIG.  2. —  Hyoid 
bone,  h\  trachea,  t; 
bronchi,  b,  b'\  larynx, 
I;  glottis,  g. 


SOME  LESSONS  ON  THE  HUMAN  BODY  5 

the  pharynx,  food  and  drink  are  beyond  a  person's  control. 
Their  movement  along  through  the  remaining  thirty  or 
more  feet  of  the  food  canal  is  due  to  the  vigorous  activity  of  the 
muscular  coats  of  the  oesophagus,  stomach,  and  intestines. 

Taste  and  smell  add  much  to  the  enjoyment  of  living. 
But  the  distribution  of  the  nerves  of  these  two  senses  in  the 
nasal  and  mouth  cavities  indicates  that  their  primary  pur- 
pose is  to  give  warning  against  the  introduction  into  the  body 
of  food,  drink,  or  air  that  is  unwholesome  or  harmful.  Not 
all  harmful  substances  have  a  bad  taste  or  odor,  nor  are  all 
substances  with  disagreeable  taste  or  odor  harmful.  How- 
ever, the  products  of  decay  in  foods  when  not  disguised  by 
spices  and  flavorings  are  likely  to  give  evidence  of  their 
presence  by  an  unnatural  odor  or  taste. 

The  tonsils  are  peculiarly  exposed  to  infection.  Their 
location  in  the  throat  is  such  that  they  are  in  contact  with 
the  air  breathed,  and  with  food  and  drink  on  its  way  to  the 
stomach.  Their  structure,  too,  is  such  as  to  make  them  sus- 
ceptible to  attacks  of  germ  diseases.  Any  " soreness"  of  the 
throat,  and  any  "patches"  upon  the  tonsils,  may  necessitate 
prompt  medical  treatment.  Many  of  the  fatal  ailments  of 
childhood  manifest  themselves  in  their  earlier  stages  by  an 
inflamed  condition  of  the  throat,  and  more  or  less  of  swelling 
and  soreness  there.  All  "colds"  should  be  regarded  with 
suspicion,  and  proper  care  and  precautions  taken  from 
their  first  appearance. 

Although  air  is  made  to  pass  in  and  out  of  the  mouth  when 
talking  and  singing,  and  when  playing  upon  some  musical 
instruments,  in  all  ordinary  breathing  the  air  should  pass  to 
and  from  the  lungs  through  the  nose.  In  this  way  cold  air 
becomes  somewhat  warmed  before  reaching  the  lungs. 
Dust  present  in  the  air  is  largely  stopped  in  the  nose,  collect- 
ing on  the  surface  of  the  moist  mucous  lining  of  the  nasal 
cavity  and  on  the  hairs  just  inside  the  nostrils. 


6  GENERAL  SCIENCE 

A  child  who  habitually  breathes  through  the  mouth  may 
be  afflicted  with  adenoids,  and  their  removal  may  become 
necessary.  Catarrh  is  a  persistent  congested  condition  of 
the  mucous  lining  of  the  nasal  cavity,  and  may  cause 
deafness. 

The  thorough  mastication  and  insalivation  of  food  is  an 
essential  stage  in  the  process  of  dissolving  it.  This  process  is 
known  as  digestion.  Water  or  other  drinks  used  to  wash 
down  the  food  do  not  take  the  place  of  the  saliva.  Man, 
unlike  birds  and  domestic  fowls,  has  no  gizzard  to  do  what 
the  teeth  should  have  done. 

The  saliva  contains  small  portions  of  a  so-called  digestive 
ferment  which  brings  about  chemical  changes  in  starchy  foods, 
converting  the  starch  into  a  form  of  sugar  which  dissolves 
easily.  The  other  digestive  fluids  also  cause  chemical 
changes  in  foods  through  the  action  of  the  ferments  which 
they  contain.  A  nervous  or  excited  state,  or  extreme 
weariness  in  body  or  mind,  interferes  with  and  may  stop  the 
secretion  of  these  digestive  fluids1,  thus  impairing  digestion. 
One  should  not  eat  at  such  times,  but  wait  until  rested  and 
quieted.  A  happy  frame  of  mind  favors  digestive  processes. 
Mealtime  should  be  a  time  of  mirth  and  social  enjoyment, 
and  never  a  time  for  controversy  and  settlement  of  disputes, 
or  for  administering  family  discipline.  The  sight,  smell, 
and  taste  of  appetizing  food,  and  a  state  of  unsatisfied 
hunger,  maintains  the  flow  of  the  digestive  fluids.  The 
flow  lessens  when  these  conditions  cease  to  exist.  Many 
people  attempting  to  speak  in  public  experience  difficulty 
from  dry  lips  and  mouth.  Their  nervousness  causes  a  less- 
ened flow  of  saliva. 

A  dry  fevered  appearance  of  the  tongue  and  mouth,  and 
a  heavy  white  or  yellowish  coating  of  the  tongue,  indicate 

1  The  amount  of  gastric  juice  secreted  per  day  may  be  five  pints  or  more. 


SOME  LESSONS  ON  THE  HUMAN  BODY  7 

a  condition  of  the  mucous  lining  of  the  stomach  and  intestines 
unfavorable  to  the  secretion  of  digestive  fluids.  In  such 
cases  one  should  eat  sparingly  till  normal  conditions  are 
restored.  Only  those  foods  should  be  eaten  which  have  been 
found  from  experience  to  be  easily  digested. 

Perhaps  no  one  condition  connected  with  the  digestion  of 
food  is  followed  by  such  a  train  of  bodily  ills  as  constipation, 
especially  where  it  persists  during  infancy,  childhood,  and 
youth.  The  whole  system  becomes  disordered  by  reason 
of  any  retention  and  reabsorption  of  bodily  wastes.  Igno- 
rance of  what  it  signifies,  and  of  the  course  to  be  pursued 
permanently  to  relieve  it,  spares  no  one  of  its  evil  conse- 
quences. Dullness  of  mind,  headache,  dizziness,  a  coated 
tongue,  and  a  foul  breath,  with  more  or  less  of  a  tired  feeling 
all  the  time,  are  some  of  the  common  results  of  constipation. 
A  full  easy  movement  of  the  bowels  daily  as  an  established 
habit  from  childhood  contributes  largely  toward  health  and 
efficiency  for  life.  Insufficient  activity  of  the  muscles  of 
the  intestines,  a  lack  in  vigor  of  their  wavelike  or  peristaltic 
movements,  is  the  immediate  cause  of  constipation. 

To  maintain  the  conditions  favorable  for  a  healthy  activity 
of  the  bowels  may  require  constant  care.  Sufficient  exer- 
cise for  the  muscles  of  the  trunk  and  abdomen,  deep  breath- 
ing, use  of  plenty  of  water  as  a  drink  between  meals1,  and 
enough  sleep,  all  contribute  to  the  general  health  and  to  a 
satisfactory  elimination  of  the  bodily  wastes.  Food  which 
repeatedly  causes  indigestion  is  to  be  avoided.  Regularity 
in  action  of  the  bowels  should,  under  all  ordinary  circum- 
stances, be  maintained  without  recourse  to  medicines. 
Meats,  eggs,  milk,  beans,  and  wheat  bread  are  some  of  the 

1  In  addition  to  the  water  taken  with  food  at  meal  times,  the  habitual  prac- 
tice of  drinking  between  meals  a  half  dozen  glasses  (three  pints)  of  water  daily 
aids  in  keeping  the  body  in  a  healthy  condition. 


8  GENERAL  SCIENCE 

foods  which  have  a  tendency  to  cause  constipation  be- 
cause of  lack  in  bulk.  Fruits  and  vegetables  generally, 
together  with  graham  flour,  corn  bread,  bran  foods,  and 
oatmeal,  are  likely  to  stimulate  the  bowels  to  a  normal 
activity. 

The  enamel  of  the  teeth  is  the  hardest  substance  in  the 
body.  It  contains  no  blood  vessels,  and  when  once  cracked 
or  broken  is  not  restored  by  nature.  The  dense  bony  mate- 
rial beneath  it,  forming  the  body  of  the  tooth  and  known  as 
dentine,  decays  when  exposed  to  the  action  of  bacteria. 
Protection  of  the  teeth  from  decay,  and  their  preservation 
throughout  life,  necessitates  continuous  care.  Frequent 
examination  by  a  competent  dentist  is  usually  advisable, 
especially  during  childhood  and  youth.  It  is  better  to  pre- 
vent decay  than  to  be  forced  to  repair  its  ravages.  There 
is  no  satisfactory  substitute  for  a  frequent  use  of  the  tooth- 
brush. As  the  first  of  the  thirty-two  teeth  in  the  permanent 
set  may  grow  into  place  when  children  are  but  six  or  seven 
years  of  age,  the  habitual  use  of  the  brush  should  begin  in 
early  childhood. 

It  is  often  possible  to  tell  much  of  a  person's  state  of  mind 
from  the  expression  of  the  lips  and  the  mouth.  The  passing 
emotions  of  mirth,  scorn,  or  disgust  are  reflected  in  one's 
face.  Discontent,  brutality,  and  vulgarity  on  the  one  hand, 
or  contentment  and  sweetness  of  disposition  on  the  other, 
stamp  themselves  indelibly  upon  the  face.  Repeated  im- 
pulses in  the  nerves  distributed  to  the  muscles  of  the  face 
leave  their  evidences  of  firmness  or  fickleness  of  purpose, 
strength  of  character  or  weakness,  in  permanent  lines  formed 
about  the  mouth.  The  kind  of  feelings  cherished,  and  the 
manner  of  thoughts  indulged,  sooner  or  later  make  or  mar 
one's  expression. 

By  means  of  the  nerves  the  varied  movements  of  the 
numerous  muscles  of  the  body  are  directed  and  controlled. 


SOME  LESSONS  ON  THE  HUMAN  BODY  9 

In  some  cases  this  is  by  direct  act  of  the  will  (mind)1,  and 
in  other  cases  such  as  movements  of  the  muscles  of  the  heart, 
diaphragm,  and  intestines,  the  action  is  largely  or  wholly 
involuntary.  It  is  over  the  nerves,  too,  that  impulses 
travel  to  the  brain  and  other  nerve  centres  giving  rise  to  sensa- 
tions. Education  as  "mind  development"  involves  for  one 
thing  an  increasing  readiness  in  interpreting  correctly  the 
significance  of  sensations. 

SUMMARY 

Any  study  of  the  mouth  cavity  must  take  into  account  that  it  is  a 
part  of  the  digestive  tract,  and  a  chief  organ  of  speech.  It  is  likewise 
the  chief  gateway  whereby  germ  diseases  enter  the  body.  The  senses 
of  taste  and  smell  may  be  considered  as  primarily  for  the  purpose  of 
preventing  entrance  of  injurious  and  poisonous  substances  into  the 
body  with  the  food  and  drink,  or  with  the  air  breathed. 

While  the  tongue  as  an  organ  of  speech  at  times  may  be  "an  unruly 
member,"  its  muscles  are  nevertheless  wholly  subject  to  one's  control. 
Its  utterances  are  what  we  make  them.  In  learning  to  speak  a  foreign 
language  there  is  much  the  same  difficulty  experienced  in  getting  the 
muscles  of  the  tongue  to  give  correct  utterance  to  sounds  as  there 
is  in  bringing  under  control  those  of  the  hand  when  learning  to  play 
musical  instruments  in  correct  time  and  with  suitable  expression. 
Sustained  and  close  attention,  and  much  practice,  may  be  necessary 
to  properly  co-ordinate  mind,  nerve,  and  muscular  action. 

1  No  one  is  likely  to  mistake  an  electric  light  bulb  for  the  electricity  by 
means  of  which  the  mechanism  of  the  bulb  produces  the  illumination.  Nor  is 
there  any  confusion  in  distinguishing  between  a  dynamo  as  a  machine,  and 
the  electrical  energy  sent  out  from  it.  In  a  similar  manner  a  sharp  distinction 
is  to  be  made  between  the  brain  as  the  organ  of  the  mind  on  the  one  hand,  and 
on  the  other  its  powers  (activities)  in  interpreting  sensations,  in  noting  rela- 
tionships among  these  sensations,  and  in  deciding  upon  a  course  of  action  in 
accordance  with  the  knowledge  possessed.  Whatever  the  nature  of  the  brain 
activity  in  the  processes  of  thought,  and  however  dependent  mental  vigor 
may  be  upon  a  well-nourished  brain,  it  simplifies  our  discussions  here  to  con- 
sider the  mind,  and  the  development  and  use  of  its  powers,  more  or  less  apart 
from  brain  phenomena. 


io  GENERAL  SCIENCE 

Great  as  the  value  of  a  good  set  of  teeth  may  be  in  the  appearance 
of  a  person,  their  primary  purpose  is  their  use  for  the  digestion  of  food. 
To  go  through  life  with  teeth  made  more  or  less  worthless  by  neglect 
in  childhood  is  a  serious  handicap  upon  health  and  length  of  life. 

THE  EYE 

The  human  eyes  when  one  stands  erect  command  a  wide 
range  of  vision  without  turning  the  head. 

The  eye  is  seldom  perfect  as  an  optical  instrument.  Its 
defects,  even  when  serious,  may  often  easily  be  remedied  by 
glasses  fitted  after  an  examination  of  the  eye  by  a  competent 
oculist.  The  eyes  of  people  whose  general  health  is  good 
give  a  lifetime  of  excellent  service  when  they  have  not  been 
subjected  to  abuse.  It  is  the  utmost  folly  not  to  give  the 
eyes  intelligent  care  especially  during  school  days.  When 
once  the  sight  is  destroyed  a  person  is  shut  away  from  much 
that  is  in  the  world  about  him.  His  knowledge  then  be- 
comes limited  largely  to  what  he  can  hear  and  touch. 

To  understand  how  it  is  that  we  can  know  of  objects  far 
distant  from  us,  and  beyond  our  reach,  requires  the  study  of 
light  as  given  in  Physics.  Through  the  transparent  interior 
of  the  eyeball  light  reaches  the  optic  nerve.  Its  terminal 
fibres  are  spread  out  over  the  interior  of  the  rear  wall  of  the 
eyeball  and  form  the  retina. 

Any  transparent  medium  with  a  curved  surface  is  a  lens. 
Those  used  in  telescopes  and  microscopes,  and  in  spectacles, 
are  of  glass.  In  the  eye  the  soft,  elastic  crystalline  lens 
serves  to  form  images  on  the  retina  just  as  the  lens  of  the 
photographer's  camera  forms  an  image  on  the  chemically 
prepared  plate.  The  cornea  (kor'-ne-ah) ,  the  vitreous  humor, 
and  the  aqueous  humor  of  the  eyeball  also  refract  light, 
i.e.,  bend  it  from  a  straight  line  course  as  it  passes  into  and 
then  out  of  them. 

An  ample  supply  of  blood  is  furnished  to  the  eyeball,  but 
the  humors,  lens,  and  cornea  are  nourished  without  dimming 


SOME  LESSONS  ON  THE  HUMAN  BODY  1 1 

their  transparency.  Circular  musular  fibres  in  the  iris 
by  their  contraction  allow  less  light  to  enter  the  eyeball, 
and  as  they  relax  the  pupil  of  the  eye  is  enlarged.  Dust  and 
any  foreign  particles  lodged  underneath  the  eyelids,  or  an 
irritation  due  to  lack  of  tear-water,  may  cause  congestion 
of  the  blood  vessels  in  the  eyeball  and  in  its  surroundings. 
This  gives  the  eye  a  temporary  blood-shot  appearance. 

Pain  in  the  eyes  as  elsewhere  in  the  body  is  nature's  warn- 
ing that  something  is  wrong  with  the  mechanism.  Weariness 
is  a  signal  for  rest,  or  a  demand  that  an  abuse  of  the  eyes 
be  stopped.  Rest  for  the  eyes  when  reading,  sewing, 

A  ' 


FIG.  3. — Formation  of  images  on  the  retina  of  the  eyeball.  (So  far 
as  the  physics  of  the  phenomenon  is  concerned  the  images  thus  formed  are 
inverted.) 

% 

or  using  the  microscope,  does  not  necessitate  complete  dis- 
use of  the  eyes.  Any  occupation  that  requires  sustained 
effort  to  see  the  same  object,  especially  if  dimly  lit  up,  soon 
wearies  the  eyes.  Looking  at  other  objects  at  different 
distances  rests  the  eyes.  The  little  muscles  that  hold  the 
lens  of  the  eye  in  a  particular  form  in  order  to  see  any  ob- 
ject distinctly  are  often  kept  under  a  strain  which  not  only 
wearies  but  weakens  them.  The  effect  is  somewhat  the  same 
as  when  one  forces  himself  to  hold  his  arm  out  horizontally 
from  the  body  for  a  long  time.  Any  serious  ailment  of  the 
eyes  calls  for  their  examination  and  possible  treatment. 
Glasses  fitted  by  oculists,  while  commonly  for  the  purpose  of 


12  GENERAL  SCIENCE 

enabling  persons  to  see  more  distinctly,  are  quite  as  often 
prescribed  to  relieve  eyestrain.  Changes  in  the  eyeball  it- 
self naturally  occur  as  a  person  grows  older,  making  necessary 
the  wearing  and  the  refitting  of  glasses  from  time  to  time. 
That  objects  at  different  distances  may  be  seen  distinctly, 
changes  in  the  form  of  the  crystalline  lens  are  continuously 


FIG.  4. — The  workers  here  are  not  likely  to  have  impaired  eyesight. 

taking  place.  This  adjustment  in  form  is  known  as  the  power 
of  "  accommodation, "  and  it  is  more  or  less  completely  lost 
in  old  age. 

A  whole  train  of  bodily  ailments  often  attend  upon  or  are 
caused  by  eyestrain.  Headaches,  nervous  exhaustion,  and 
impaired  digestion  are  often  directly  traceable  to  it.  Im- 
patience and  ill-temper  may  arise  from  it.  No  one  should 
be  ignorant  of  what  constitutes  right  conditions  for  continu- 
ous use  of  the  eyes,  especially  any  close  application  of  them. 


SOME  LESSONS  ON  THE  HUMAN  BODY 


Reading  when  weary,  or  when  on  trains,  or  when  lying  down, 
severely  taxes  the  eyes  and  should  be  avoided.  Large  re- 
sponsibilities rest  upon  architects  and  builders  whose  business 
it  is  to  arrange  both  for  the  artificial  and  for  the  natural 
lighting  of  the  rooms  and  buildings  in  which  people  are  to 
live  and  work. 

It  is  not  especially  important  that  objects  in  front  of 
pupils  in  schoolrooms,  and  of  workers  in  offices  and  shops 
and  homes,  shall  be 
illuminated  by  light 
that  "comes  over  the 
left  shoulder."  But 
the  illumination  must 
be  neither  too  bright 
nor  too  dim,  and  the 
light  must  be  so  uni- 
formly diffused  that 
sharply  outlined  shad- 
ows do  not  exist  in 
the  room.  Any  con- 
scious effort  in  excluding 
light  from  the  eyes 
because  it  is  too  glaring, 

or  in  making  out  details  of  objects  viewed  because 
the  light  is  too  dim,  is  evidence  of  something  wrong 
with  the  illumination  of  the  room.  No  direct  rays 
of  light  should  be  allowed  to  come  into  the  eyes  either 
from  the  sun  or  from  electric  bulbs.  The  contraction  of 
the  pupil  to  shut  out  the  excess  of  light  from  an  unscreened 
lamp  shining  directly  into  one's  eyes  may  result  in  eyestrain, 
since  too  little  light  can  then  enter  them  from  the  objects 
upon  which  one  is  at  work.  The  glare  of  the  lights  of  an 
automobile  blinds  one  to  other  objects  near  at  hand  that  are 
not  brightly  lit  up,  because  the  size  of  the  pupil  of  the  eye 
adjusts  itself  to  the  more  intense  light. 


FIG.  5. — Hard  on  the  eyes. 


14  GENERAL  SCIENCE 

School  requirements  for  use  of  the  eyes  are  at  times  ex- 
acting but  these  requirements  are  never  sufficient  excuse  for 
permanent  impairment  of  vision,  nor  for  long-continued 
eyestrain.  Since  schools  do  demand  so  much  in  a  sustained 
use  of  the  eyes,  it  is  the  more  necessary  that  all  contributing 
causes  to  weakened  eyesight  such  as  late  hours,  motion  pic- 
tures, etc.,  be  largely  avoided.  Special  care  should  be  given 
to  maintain  good  health,  and  when  necessary  to  be  correctly 
fitted  with  glasses.  Under  no  circumstances  should  use 
of  the  eyes  upon  difficult  work,  or  under  unfavorable  con- 
ditions, be  continued  after  the  eyes  have  become  inflamed, 
or  have  begun  to  ache  from  use,  or  when  headache  occurs 
from  eyestrain. 

SUMMARY 

While  the  eye  as  an  optical  instrument  may  be  conside  ed  perfect 
in  its  design,  it  is  probable  that  relatively  few  people  are  free  of  defects 
in  eyesight.  Most  such  defects  are  of  minor  character,  and  may 
oftentimes  be  ignored.  However,  when  the  general  health  is  impaired, 
or  when  excessive  and  exacting  use  is  made  of  the  eyes,  these  defects 
may  become  serious.  Impaired  eyesight  is  a  handicap  in  life's  activi- 
ties and  in  its  enjoyments. 

Intelligent  care  of  the  eyes  requires  a  knowledge  of  their  structure, 
their  defects,  and  their  proper  use. 

Eyestrain  may  be  caused  by  dim  lighting,  by  too  glaring  lights,  and 
by  unequal  diffusion  of  light.  Fatigue  and  exhaustion  of  the  whole 
nervous  system  may  follow,  upsetting  the  equilibrium  of  the  body 
organism  and  resulting  in  a  disordered  state  of  the  nerves  and  a  loss 
of  mental  poise. 

The  small  muscles  whose  office  is  to  hold  the  crystalline  lens  in 
that  particular  form  where  vision  is  most  distinct  become  exhausted 
by  long-sustained  close  application,  such  as  in  reading  fine  print,  in 
continuous  use  of  the  microscope,  and  in  doing  fine  sewing.  This 
strain  is  relieved  if  from  time  to  time  the  eyes  are  used  in  looking  at 
other  and  more  distant  objects.  Many  headaches  from  which  people 
suffer  are  directly  or  indirectly  caused  by  eyestrain. 


SOME  LESSONS  ON  THE  HUMAN  BODY 


Pupils  not  infrequently  acquire  at  school  the  bad  habit  of  stooping 
or  bending  over  their  books.  This  strains  the  eyes  by  bringing  them 
too  close  to  the  print.  Twelve  inches  is  about  the  proper  distance. 

Exercises 

1.  By  what  means  is  a  wide  variety  in  movement  of  hand  and  fingers 
secured? 

2.  Tell  the  location,  form,  manner  of  growth,  and  uses  of  the  finger  nails. 

3.  Name  several  of  the  structures  within 
the  hand  of  which  something  can  be 
learned  by  inspection  though  they  are 
hidden  from  view. 

4.  Define  (a)  tonsillitis;  (b)  adenoids. 

6.  What  information  concerning  the 
state  of  one's  health  can  be  learned 
from  the  appearance  of  the  tongue? 
In  what  sense  is  the  tongue  an  organ 
of  digestion? 

6.  Describe    (a)    the    hyoid    bone    as   to 
its  position  and  use;   (b)  the  pharynx 
as  to  position  and  structure. 

7.  Why  do  the  teeth  ache?    How  is  nourish- 
ment conveyed  into  a  tooth? 

8.  How    does    a   singer   become   able    to 

produce  any  note    desired  in  singing         PIG.    6. — Tests  for   astigma- 
and   a   speaker   to  utter  any    desired     tism.    Hold  the  cut  at  a  suitable 


sound  in  speech? 


distance  from  the  eyes   and  in 

A  a    good    light.       Note    if     the 

9.  About  what  is  the  diameter  of  the  eye-     parallel  lines  in  all  directions 

ball   (a)   side  wise;   (b)   up  and  down?     appear  equally  distinct. 

By  a  drawing  indicate  the  relative  size 

and   form    of    the    upper   and  lower    eyelids    as  seen  when  the  eye 

is  "open." 

10.  What  usually  becomes  of  the  tear-water  that  drains  off  into  the  nose 

through  the  tear-duct?  How  are  the  frequent  movements  of  the  eye- 
lids caused?  What  is  meant  by  saying  that  these  movements  are 
commonly  "involuntary?" 

11.  What  are  common  defects  in  the  eyeballas  an  optical  instrument? 

12.  What  is  generally  true  of  the  eyesight  when  it  is  once  harmed  by  reckless 
or  ignorant  use  of  the  eyes?     Explain  the  purpose  of  the  ciliary  (sil'- 
e-ar-e)  muscles.     State  how  they  become  weakened,  and  how  this  may 
be  avoided  without  disuse  of  the  eyes. 


II.  HEAT  IN  RELATION  TO  THE  HUMAN  BODY 

COMBUSTION 

For  a  complete  understanding  of  the  changes  known  as 
combustion  one  must  study  Chemistry.  Combustion  com- 
monly means  oxidation,  i.e.,  union  with  oxygen  (O),  accom- 
panied by  noticeable  heat  and  light  as  result  of  the  chemical 
change.  Coal  is  largely  carbon  (C),  and  when  it  burns 
(oxidizes)  one  of  the  products  is  a  gas  known  as  a  carbon  dioxide 
whose  chemical  formula  is  CO2.  When  the  gas  hydrogen  (H)  is 
burned,  the  product  is  water  (H2O).  Paraffine,  tallow,  wood, 
kerosene,  and  many  other  substances  used  for  fuel  and 
lights,  contain  carbon  and  hydrogen  in  their  chemical  com- 
position. When  burned  they  yield  both  water  and  carbon 
dioxide  as  the  principal  products  of  their  combustion.  Oxy- 
gen exists  free  in  the  air  mixed  with  about  four  times  its 
volume  of  nitrogen. 

Oxygen  as  an  element  in  water  is  so  much  heavier  than 
hydrogen  that  eight-ninths  by  weight  of  all  water  is  oxygen. 
It  is  calculated  that  oxygen  constitutes  about  one-half  the 
weight  of  the  chemical  compounds  forming  the  rocks  of  the 
earth's  crust. 

One  of  the  most  important  teachings  of  chemistry  is  that 
the  same  substance  is  always  made  up  of  the  same  chemical 
elements,  and  that  these  are  always  united  in  the  same  propor- 
tions by  weight.  The  compound  known  as  water  has  the 

16 


HEAT  IN  RELATION  TO  THE  HUMAN  BODY  17 

formula  H2O  whether  it  is  a  liquid,  or  a  solid  such  as  ice 
and  snow  and  frost,  or  the  invisible  vapor  present  at  all 
times  in  the  air  about  us.  The  relative  weights  of  oxygen 
and  hydrogen  in  it  remain  unchanged. 

When  coal  burns  with  a  limited  supply  of  oxygen  a  poi- 
sonous gas  called  carbon  monoxide  (CO)  forms.  In  the  pres- 
ence of  more  oxygen  this  gas  burns  with  a  bluish  flame  form- 
ing carbon  dioxide.  This  flame  is  often  seen  above  a  coal 
fire.  The  illuminating  gas  furnished  in  towns  and  cities  for 
fuel  and  lights  contains  more  or  less  carbon  monoxide,  and 
any  leakage  of  gas  from  burners  or  from  stoves  is  dangerous 
because  of  its  poisonous  effects  as  well  as  its  explosive  na- 
ture when  mixed  with  air. 

Oxidation  may  go  on  very  slowly  wherever  uncombined  oxy- 
gen comes  in  contact  with  substances  with  which  oxygen 
unites  readily.  This  slow  combustion  occurs  within  water, 
and  it  goes  on  in  the  cells  of  the  body.  The  heat  liberated  in 
the  various  tissues  ordinarily  maintains  a  temperature  of 
the  human  body  above  that  of  the  surrounding  atmos- 
phere. In  some  animals  like  the  turtle  and  the  snake  this 
oxidation  is  so  slow  that  they  always  feel  cold  when  handled 
because  their  body  temperature  is  less  than  that  of  human 
beings. 

In  the  rusting  of  such  metals  as  iron,  oxidation  takes  place 
very  slowly;  in  the  explosive  mixture  of  gasoline  vapor  or  of 
illuminating  gas  with  air,  it  may  be  instant  and  violent. 
Many  of  the  high  explosives  used  in  blasting  have  in  their 
composition  sufficient  oxygen  to  make  it  possible  for  combus- 
tion to  occur  away  from  the  air. 

The  temperature  to  which  bodies  like  kerosene,  wood,  and 
coal  must  be  brought  in  order  that  combustion  may  occur  is 
called  the  kindling  temperature,  or  point  of  ignition. 

A  flame  is  a  burning  gas  or  vapor.  A  candle  flame  ceases 
to  exist  at  its  outer  surface  where  combustion  is  complete. 


1 8  GENERAL  SCIENCE 

On  the  inside  the  flame  begins  where  the  kindling  tempera- 
ture of  the  supply  of  gas  or  vapor  has  been  reached,  and 
where  oxygen  is  available  for  combustion.  The  candle  flame 
has  the  form  of  a  hollow  cone,  enclosing  a  cone  of  vapor  that 
is  not  burning.  The  blowpipe  flame  is  hot  because  the  same 
amount  of  combustion  occurs  within  a  smaller  space. 

The  color  of  different  lights  is  largely  due  to  the  kind  of 
material  that  is  incandescent  (light  giving),  and  to  the  tem- 
peratures to  which  this  material  is  heated.  In  the  common 
electric  bulb  there  is  no  combustion,  the  bulb  having  no 
oxygen  inside  of  it.  The  temperature  of  the  filaments 
caused  by  the  electric  current  is  sufficiently  high  to  produce 
incandescence. 

SUMMARY 

The  term  combustion  in  opular  usage  means  a  case  of  oxidation 
where  the  heat  liberated  causes  burning  material  to  become  so  hot  as 
to  give  off  light. 

The  products  of  oxidation  are  known  as  oxides.  They  may  be  gases 
as  carbon  dioxide,  or  liquids  as  water,  or  solids  as  iron  rust. 

A  flame  is  a  gas  or  vapor  that  is  burning.  The  combustion  may  be 
slow  and  under  control,  or  it  may  be  instant  and  explosive  in  violence. 
The  size  of  a  flame  is  determined  by  the  distance  outward  to  which 
the  mixture  of  the  gaseous  material  with  air  extends. 

In  a  candle  flame  the  inner  dark  cone  consist  of  vapor  not  burning 
because  of  lack  of  oxygen,  and  because  its  temperature  is  below  the 
point  for  ignition.  The  hollow  luminous  cone  is  burning  vapor,  the 
outermost  limits  of  which  are  almost  colorless  by  reason  of  an  almost 
completed  combustion. 

Carbon  dioxide  gas  from  the  air  is  used  by  plants  in  the  manufacture 
of  such  materials  as  sugar,  starch,  and  wood  fibre.  But  it  must  not 
be  overlooked  that  plants,  like  animals,  must  have  a  supply  of  oxygen 
to  maintain  their  life,  and  to  provide  the  energy  necessary  for  their 
growth.  The  amount  of  carbon  dioxide  given  off  as  a  product  of  this 
plant  breathing  is,  however,  insignificant  in  comparison  with  the 
amount  converted  by  the  plant  into  wood,  starch,  and  sugar. 


HEAT  IN  RELATION  TO  THE  HUMAN  BODY  19 

PURE  AIR  AND  BREATHING1 

In  order  to  keep  warm  and  dry  men  require  shelter  from 
the  weather.  The  occupations  of  many  people  keep  them 
within  doors  the  year  around.  As  a  matter  of  economy  and 
of  comfort  during  the  winter  season,  dwellings  and  places  of 
business  are  guarded  against  the  entrance  of  the  cold  outer  air. 
This  shuts  away  the  supply  of  oxygen  essential  to  health. 
A  single  gas  light  exhausts  the  oxygen  of  a  room  and  produces 


FIG.   7. — Sleeping  porch,  and  sun  parlor. 

carbon  dioxide  as  fast  as  the  breathing  of  several  persons. 
So  far  as  need  of  air  is  concerned  man  is  an  out-of-door  ani- 
mal. The  conditions  of  civilized  life  have  shut  him  in  so 
closely  that  health  is  often  impaired,  and  life  itself  sometimes 
sacrificed. 

About  one-third  of  a  person's  life  should  be  spent  in  sleep. 
For  sleep  to  be  most  refreshing  and  invigorating  it  should  be 
in  rooms  or  porches  wide  open  to  the  out-of-doors  air.  Only 

1  Respiration  as  the  term  is  used  in  biology  involves  the  process  of  oxidation 
as  it  occurs  in  the  cells.  It  is  a  function  of  living  cells  wherever  located.  On 
the  other  hand  the  term  breathing  is  restricted  to  the  exchange  of  gases  within 
and  without  plants  and  animals,  and  is  a  purely  physical  process. 


20  GENERAL  SCIENCE 

extreme  cold  or  dampness  is  excuse  for  sleeping  temporarily 
shut  away  from  an  abundance  of  outside  air.  An  open  but 
well-screened  sleeping  porch,  with  a  warm  room  to  dress  in 
when  the  weather  is  cold,  makes  quite  an  ideal  condition. 

During  the  day  the  ordinary  activities  of  life  render  un- 
necessary any  special  attention  to  ventilation  save  where  large 
numbers  of  people  are  together  as  in  public  halls,  schools, 
and  factories.  In  these  places  there  is  likelihood  of  oxygen 
starvation.  The  air,  too,  soon  becomes  laden  with  moisture 
from  perspiration,  and  from  water  in  the  respired  air.  Dis- 
ease germs  may  be  given  off  into  the  air  from  any  infected 
person  present.  All  this  makes  necessary  the  continuous 
renewal  of  the  indoors  air.  In  cold  weather  air' from  out  of 
doors  should  be  warmed  before  it  is  allowed  to  spread  through 
the  rooms.  There  should  never  be  appreciable  currents 
(drafts)  in  any  part  of  a  room.  The  air  should  always  be 
free  from  dust,  too,  and  should  contain  considerable  mois- 
ture, especially  if  it  is  furnace  heated.  A  humidity  of  from 
40  per  cent  to  50  per  cent  does  not  dry  the  mucous  mem- 
branes of  the  air  passages,  nor  does  it  interfere  with  evapora- 
tion of  the  perspiration. 

To  maintain  the  circulation  necessary  to  bring  a  continu- 
ous supply  of  air  into  rooms,  advantage  is  usually  taken  of 
the  fact  that  air  when  heated  becomes  less  dense  (lighter). 
The  air  of  a  building  may  be  kept  in  circulation  by  having 
one  portion  warmer  than  other  parts  of  it.  The  colder  and 
more  dense  air  presses  the  warmer  air  onward  and  outward. 
The  chapters  on  heat  and  pneumatics  (nu-mat'-iks)  in 
Physics  usually  include  a  study  of  air  currents,  and  of  sys- 
tems of  heating  and  of  ventilating.  The  satisfactory  ven- 
tilation of  the  many  rooms  in  large  buildings  used  for  offices, 
stores,  factories,  or  for  schoolroom  purposes,  requires  that 
air  be  forced  into  them  or  withdrawn  from  them  by  some  me- 
chanical means,  such  as  fans  driven  by  electricity.  This 


HEAT  IN  RELATION  TO  THE  HUMAN  BODY 


21 


air  in  some  cases  is  made  to  pass  through  a  room  where  in 
some  one  of  various  ways  it  is  " washed"  free  of  dust  and 
other  impurities,  and  given  the  desired  amount  of  moisture. 
In  winter  it  may  then  be  warmed  by  passing  it  over  steam 
coils  before  distribution  in  the  building,  and  in  summer  it 
may  be  cooled  by  use  of  ice.  Continuous  stirring  of  air 
that  is  not  changed  in  any  other  way  has  been  found  to  afford 
marked  relief  in  ill-ventilated  rooms.  The  movement  of  the 


FIG.  8. — Framework  of  the  chest  walls.  In  B  the  chest  cavity  has  been 
enlarged  by  the  contraction  of  the  rrmscular  walls;  and  in  A  decreased  by  the 
relaxation  of  these  same  muscles. 

air  lessens  the  discomfort  and  sense  of  depression  occasioned 
by  having  warm  moisture-laden  air  remain  stagnant  around 
a  person. 

Serving  as  a  partition  between  the  chest  and  abdominal 
cavities  the  diaphragm  (di'-a-fram)  is  attached  at  its  circum- 
ference to  the  side  walls  of  the  chest.  The  framework  of  the 
chest  is  made  up  of  the  ribs,  the  spine,  and  the  breast-bone. 
The  muscular  fibres  of  the  diaphragm  are  so  arranged  that 
it  is  flattened  downward  when  they  contract,  thus  crowding 
the  stomach,  liver,  and  intestines  outward  and  enlarging  the 
chest  cavity.  Not  least  among  the  beneficial  effects  of  deep 


22 


GENERAL  SCIENCE 


breathing,  involving  as  it  does  the  full  use  of  the  diaphragm, 
is  the  rhythmic  pressure  exerted  downward  upon  the  stomach 
and  liver.  This  promotes  digestion,  and  tends  to  prevent 
constipation.  Over  the  motions  of  this  muscle  which  is  so 
largely  concerned  in  breathing  a  person  has  but  slight  and 
indirect  control,  making  the  action  in  large  part  involuntary. 
The  muscles  of  the  side  walls  of  the  chest  are,  however, 
largely  under  control.  By  throwing  back  the  shoulders, 

and  by  causing  the  muscles  be- 
tween the  ribs  to  contract  and 
pull  the  ends  of  the  lower  ribs 
apart,  the  chest  cavity  can  be 
considerably  enlarged  at  will. 
An  easy  erect  position,  whether 
sitting  or  walking,  gives  larger 
space  for  the  lungs  than  where 
one  goes  about  stooped  and 
with  drooping  shoulders.  Per- 
sistent efforts  to  fully  inflate 
the  lungs  in  breathing  is  one 
of  the  ways  of  maintaining 
health.  It  is  the  unused  por- 
tions of  the  lungs  that  are  most 
likely  to  become  diseased. 

The  lung  capacity  in  use  is  about  200  cubic  inches  (3200 
cc.).  Only  about  one-eighth  of  this  amount  passes  in  and 
out  at  each  breath1.  The  reserve  supply  of  air  not  exhaled 
at  every  breath  serves  to  prevent  sudden  changes  of  tempera- 

1  The  following  tabulation  exhibits  approximately  the  air  volumes  con- 
cerned in  breathing: 

Air  passing  in  and  out  at  each  breath  (Tidal  Air) 20-30  cu.  in. 

Additional  air  that  can  be  but  seldom  is  taken  in  (Comple- 

mental  Air) 120  cu.  in. 

Air  that  can  be  forced  out  after  a  full  inspiration 150-250  cu.  in. 

Air  that  cannot  be  driven  out  (Residual  Air) 100  cu.  in. 


FIG.  9. — Wrong  sitting  position. 
The  lungs  cannot  be  fully  inflated 
in  breathing. 


HEAT  IN  RELATION  TO  THE  HUMAN  BODY  23 

ture  in  the  lungs  as  cold  air  is  inhaled,  and  to  prevent  death 
by  suffocation  when  temporary  stoppage  of  the  air  passages 
occurs. 

Air  may  be  rebreathed  repeatedly  and  continue  to  furnish 
oxygen  to  maintain  life.  But  it  is  to  be  remembered  that 
exhaled  air  containing  available  oxygen  may  be  unfit  for  use 
because  of  the  carbon  dioxide,  water  vapor,  and  waste  organic 
matter  in  it.  The  air  as  inhaled  commonly  consists  of  about 
21  per  cent  oxygen,  78  per  cent  nitrogen,  i  per  cent  argon, 
and  3/100  per  cent  carbon  dioxide  gas,  along  with  a  varialbe 
quantity  of  water  vapor  and  dust  particles.  The  exhaeld 
air  is  saturated  with  moisture,  and  has  approximately  16 
per  cent  oxygen  and  5  per  cent  carbon  dioxide,  the  argon 
and  nitrogen  gases  remaining  unchanged  in  amount.  About 
one  pint  of  water  passes  from  the  body  daily  as  vapor  in  the 
breath. 

The  need  of  ventilation  is  often  apparent  to  a  person  enter- 
ing a  schoolroom  or  public  hall  when  those  in  the  room  are 
unaware  of  the  bad  condition  of  the  air.  Dullness,  rest- 
lessness in  body,  headaches,  inability  to  give  continuous  at- 
tention, and  much  of  the  feeling  of  irritation  experienced  by 
those  shut  up  in  schoolrooms  oftentimes  disappear  after  a 
few  minutes  of  exercise  indoors  with  windows  wide  open. 
It  is  to  be  remarked  that  cold  air  is  not  necessarily  pure  air, 
rior  do  rooms  need  ventilating  because  they  are  comfortably 
warm.  Pure  air,  however,  is  no  cure  for  late  hours  and  in- 
sufficient sleep,  or  for  lack  of  wholesome  food  and  absence 
of  other  conditions  essential  to  sound  bodies  and  bright 
minds. 

Artificial  breathing  in  cases  of  drowning  may,  if  necessary, 
be  successfully  maintained  for  a  long  period  by  laying  the 
patient  face  down,  the  face  turned  to  one  side,  and  the  mouth 
open  to  admit  free  passage  of  air  to  and  from  the  lungs. 
Sitting  astride  the  hips  of  the  patient  let  some  strong  person 


24  GENERAL  SCIENCE 

alternately  apply  and  then  remove  pressure  upon  the  lungs 
through  the  walls  of  the  chest.  This*  may  be  accomplished 
by  holding'the  hands  against  the  lower  ribs  and  throwing  the 


FIG.   10. — Resuscitation  of  the  drowned — expiration  in  artificial  breathing. 


PIG.   ii. — Resuscitation  of  the  drowned — inspiration  in  artificial  breathing. 

weight  of  the  body  first  forward  and  then  backward  with 
about  the  same  rhythm  as  in  natural  breathing. 

SUMMARY 

Ventilation  seeks  to  secure  an  ample  supply  of  oxygen  for  respiration, 
and  at  the  same  time  to  prevent  the  air  about  a  person  from  becoming 


HEAT  IN  RELATION  TO  THE  HUMAN  BODY  25 

unduly  laden  with  moisture,  with  carbon  dioxide,  and  with  organic 
matter  thrown  off  from  the  body  in  the  breath.  A  continuous  renewal 
of  the  air  in  closed  living  rooms,  offices,  and  assembly  halls  is  necessary. 

The  problem  of  ventilation  becomes  a  serious  one  only  during 
weather  when  rooms  are  kept  tightly  closed  on  account  of  the  cold. 
All  unnecessary  outlays  for  heating  buildings  must  be  avoided,  and 
all  drafts  of  cold  air. 

Particular  attention  should  be  given  to  securing  an  abundance  of 
pure  air  during  the  hours  of  sleep.  It  is  a  relatively  easy  matter  to 
provide  sufficient  bedding  to  protect  against  any  danger  of  being  chilled 
while  asleep  in  a  room  open  to  out-of-doors  air  even  in  the  coldest 
weather. 

More  serious  than  the  dullness  of  mind  and  the  weariness  of  body 
due  to  oxygen  starvation  when  sleeping  in  poorly  ventilated  rooms  is 
the  lack  of  bodily  vigor,  and  the  lessened  powers  of  resistance  to  germ 
diseases.  This  menace  to  health  is  the  greater  because  the  relation- 
ship is  not  always  apparent,  and  because  the  ill  consequences  are  often 
long  delayed. 

The  development  of  tuberculosis  in  a  person  could  often  have  been 
prevented  by  the  same  care  that  is  exercised  later  in  an  effort  to  effect 
a  cure  through  being  much  out-of-doors,  and  by  having  suitable  em- 
ployment, sufficient  exercise,  and  nourishing  food. 

In  the  rhythmic  rise  and  fall  of  the  diaphragm  nature  has  provided  an 
important  means  of  continuously  stimulating  muscular  action  in  the 
digestive  tract,  and  of  preventing  constipation. 

Lung  capacity  varies  much  in  different  persons,  and  as  a  rule  is  con- 
siderably more  in  a  man  than  in  a  woman.  It  is  disuse  of  the  lung 
capacity,  however,  that  is  the  really  serious  consideration.  Laziness 
in  breathing  should  be  overcome,  but  forced  and  intermittent  efforts 
to  do  this  accomplish  but  little.  There  should  be  enough  of  active 
daily  exercise  to  cause  a  demand  by  the  body  for  an  increased  supply 
of  oxygen,  thus  necessitating  deeper  breathing. 

The  chances  for  life  at  times  of  choking  or  of  drowning  may  depend 
upon  the  reserve  air  in  the  lungs.  Everyone  should  know  just  how  to 
proceed  to  resuscitate  a  drowned  person. 

THE  HUMAN  BODY  AS  AN  ENGINE,  AND  THE  REGU- 
LATION OF  BODY  TEMPERATURE 

The  fact  that  a  person  can  do  work  and  can  move  about 
presupposes  the  existence  of  energy  by  use  of  which  these 


26 


GENERAL  SCIENCE 


activities  and  labors  are  performed.  Energy  is  often  denned 
as  that  by  use  of  which  work  is  done.  Any  machine  such  as 
an  engine,  is  only  a  means  employed  for  using  energy  to  do 
work.  The  human  body  comes  under  this  definition,  and 
this  conception  of  the  body  includes  brain  activities  as  well 
as  muscular  effort. 

The  human  body  as  a  living  organism  possesses,  however, 
the  power  of  repairing  itself  under  right  conditions  of  liv- 
ing. If  properly  cared  for,  it  should 
neither  break  down  nor  wear  out  till  long 
past  the  allotted  "three  score  years  and 
ten."  As  with  any  other  engine  the 
character  and  quantity  of  work  it  can  do 
depends  in  large  measure  upon  the  care  it 
has,  and  the  good  judgment  exercised 
in  its  use.  Folly,  ignorance,  and  inex- 
perience all  combine  to  impair  its  use- 
fulness or  to  wreck  it  altogether.  It  is 
one  of  the  purposes  of  schools  to  give  in- 
struction and  training  in  the  right  uses 
as  a  machine  may  of  both  body  and  mind.  Success  in  living 

break     down     rather  ... 

than  wear  out.  even   as  success  in  business  requires  the 

best  use  of  all  the  means  and  machinery 
of  life.  It  is  necessary  for  the  well-being  of  an  individual  that 
the  bodily  processes  be  under  as  intelligent  control  and  as 
constant  care  as  that  exercised  by  an  engineer  with  a  locomo- 
tive, or  by  a  chemist  in  laboratory  experiments. 

The  body  like  the  steam  engine  depends  upon  energy  lib- 
erated within  it  by  chemical  changes.  A  considerable  por- 
tion of  this  energy  is  used  in  keeping  up  the  bodily  processes. 
The  activities  of  the  heart,  digestive  organs,  brain,"  and  other 
organs  require  an  expenditure  of  energy.  Deficiency  in 
its  amount  means  imperfect  performance  or  complete  ces- 
sation in  their  activities.  It  is  chiefly  the  starchy  foods, 


FIG.  12.— The  body 


HEAT  IN  RELATION  TO  THE  HUMAN  BODY  27 

sugars,  and  fats  that  are  body  fuels.  On  the  other  hand,  one- 
seventh  or  more  of  the  food  needed  by  the  body  is  required 
for  rebuilding  the  various  tissues.  Foods  that  serve  this  spe- 
cial purpose  are  known  as  proteins.  Starch,  sugars,  and  fats 
are  classed  as  carbohydrates.  The  energy  from  oxidation  in 
the  body  maintains  a  temperature  necessary  for  the  various 
organs  to  perform  their  several  functions  (duties) .  The  chem- 
ical products  of  this  oxidation  in  the  body,  even  as  in  the 
combustion  of  coal  or  oil,  are  largely  carbon  dioxide  and 
water. 

Most  of  the  processes  within  the  body  are  normally  carried 
on  without  conscious  effort.  If  it  were  necessary  to  give 
attention  to  every  act  in  respiration,  or  to  attend  to  what  is 
now  the  involuntary  action  of  the  heart  muscles,  little  else 
could  be  done.  One  might  forget  to  breathe,  or  to  keep 
the  heart  beating  regularly.  Freed  from  the  necessity  of 
directing  the  bodily  mechanism,  the  mind  can  be  employed  in 
directing  the  expenditure  of  the  excess  energy  of  the  body  in 
those  physical  and  mental  efforts  involved  in  earning  a 
livelihood  or  in  promoting  culture,  health,  and  happiness. 

The  living  matter  contained  in  the  cells  of  the  different 
body  tissues  cannot  endure  any  considerable  change  in  tem- 
perature without  harm  to  it  and  possible  destruction  of  its 
life.  One  of  the  functions  of  the  skin  through  secretion  of 
perspiration  is  to  regulate  the  body  temperature  so  that  in 
health  it  varies  but  little  summer  or  winter,  regardless  of 
whether  one  is  indoors  or  out.  As  the  perspiration  evaporates 
from  the  surface  of  the  body  heat  is  required  to  vaporize  the 
water.  This  heat  is  provided  in  part  from  the  body,  and 
the  more  profuse  the  perspiration  and  the  more  complete 
its  vaporization,  the  larger  is  the  amount  of  heat  taken  from 
the  body.  The  higher  the  body  temperature  as  result  of 
jnuscular  exercise  the  more  active  is  the  secretion  of  perspi- 
ration by  the  glands  in  the  skin.  It  is  nature's  provision  that 


28  GENERAL  SCIENCE 

the  more  heat  there  is  in  the  body  the  more  there  is  disposed 
of  in  this  way;  the  lower  the  body  temperature,  the  less  ac- 
tive is  the  secretion  of  perspiration  and  the  less  the  loss  of 
heat  with  it. 

Since  the  temperature  of  the  body  is  commonly  higher  than 
that  of  the  surrounding  atmosphere,  there  is  also  a  loss  of 
heat  direct  to  the  air  from  the  warm  body  just  as  in  the  cool- 
ing of  any  other  heated  object.  By  use  of  suitable  clothing 
protection  may  be  had  from  the  dangers  incident  to  chilling 
the  body  surface,  and  depriving  the  skin  of  its  blood  supply. 
If  one  gets  chilled  the  internal  organs  become  congested 
(overfilled)  with  blood  that  should  have  been  distributed 
to  the  surface  and  extremities  of  the  body.  The  regulation 
of  body  temperature  by  the  skin  is  interfered  with,  and  the 
disordered  condition  of  the  body  known  as  a  "cold"  may 
result.  Oftentimes  this  develops  into  dangerous  ailments 
such  as  pneumonia,  or  into  an  inflamed  state  of  organs  other 
than  the  lungs. 

Exposure  at  the  throat  and  upper  part  of  chest  is  especially 
dangerous  when  the  lungs  are  themselves  filled  with  cold 
air.  There  should  be  especial  attention  given  to  the  cir- 
culation of  blood  in  the  extremities  of  the  body.  The  feet 
and  hands  should  be  warm  at  all  times.  Wet  or  damp  cloth- 
ing not  only  wastes  body  heat  by  vaporization  of  the  mois- 
ture, but  clothing  when  damp  conducts  heat  from  the  body 
much  faster  than  when  dry.  After  a  bath  the  body  should 
be  vigorously  rubbed  with  a  dry  towel  till  its  surface  is  com- 
pletely dry.  This  avoids  any  chill  due  to  abstraction  of 
heat  from  the  body  as  water  on  the  skin  vaporizes.  The 
rubbing  should  result  in  a  redness  of  the  skin.  A  feeling  of 
warmth,  together  with  a  "glow"  of  the  skin,  follows  an  in- 
crease in  the  amount  of  blood  sent  to  the  body  surface  as 
result  of  the  irritation  produced  by  the  rubbing.  The  chill 
experienced  when  leaving  over-heated  rooms,  or  crowded 


HEAT  IN  RELATION  TO  THE  HUMAN  BODY  29 

assembly  halls  with  their  moisture-laden  air,  may  be  due  in 
part  to  the  evaporation  of  perspiration  from  the  clothing. 

SUMMARY 

The  human  body  as  an  instrument  for  doing  work  may  very  properly 
be  considered  a  machine.  Its  care  in  order  to  secure  the  largest  service 
from  it  requires  a  degree  of  intelligence  surpassing  that  needed  generally 
in  the  management  of  machinery.  Conditions  must  be  maintained 
favorable  to  its  repair  through  growth.  Undue  destruction  of  its  parts 
by  excessive  or  improper  use  must  be  avoided.  Proper  balance  must 
be  maintained  between  its  waste  and  repair. 

Any  impairment  of  the  powers  of  the  body  is  a  serious  handicap 
throughout  life.  The  harm  due  to  ignorance  is  just  as  serious  as  though 
done  by  deliberate  choice.  Much  of  the  ill-health  of  later  life,  and 
many  of  the  limitations  of  the  body  in  its  usefulness  as  a  machine,  are 
often  directly  traceable  to  an  unwise  manner  of  living  during  childhood 
and  youth. 

All  motion  occurring  in  the  body  in  the  performance  of  work  involves 
an  expenditure  of  energy.  All  the  activities  of  digestion,  respiration, 
and  circulation,  together  with  those  of  the  brain  and  nervous  system 
as  a  whole,  require  a  supply  of  energy  without  which  the  bodily  proc- 
esses would  cease. 

The  temperature  of  the  body  is  maintained  by  chemical  changes 
within  the  body  known  as  oxidation.  Any  considerable  departure 
from  a  normal  temperature  of  98°  F.  makes  impossible,  too,  a  continu- 
ance of  the  bodily  processes,  and  death  results. 

One  of  the  chief  functions  of  the  skin  is  the  regulation  of  body 
temperature  by  disposing  of  any  excess  of  bodily  heat  in  the  vaporiza- 
tion of  perspiration.  When  by  reason  of  old  age,  wasting  disease, 
impaired  digestion  or  assimilation,  the  temperature  of  the  body  runs 
much  below  normal,  extra  clothing  must  be  worn  and  warmth  from 
without  the  body  must  be  provided. 

Colds  may  result  from  a  bodily  state  of  depression  due  to  fatigue. 
At  such  times  germs  lodged  in  the  lungs  and  nasal  passages  are  given 
opportunity  for  rapid  development  because  of  the  lessened  powers  of 
resistance  of  the  body.  Colds  may  be  the  result  of  a  congested  and 
inflamed  condition  of  the  nasal  passages,  stomach,  intestines,  or  kid- 
neys, due  to  an  excessive  blood  supply  sent  to  them  at  a  time  when  the 
surface  of  the  body  is  thoroughly  chilled.  Whatever  promotes  an 


30  GENERAL  SCIENCE 

active  circulation  of  the  blood  in  all  parts  of  the  body,  and  whatever 
contributes  to  the  general  good  health,  aids  in  the  prevention  of  colds. 

Exercises 

1.  To  what  is  the  color  of  candle  and  lamp  flames  largely  due?     What  is  the 
nature  of  the  " smoke"  from  chimneys? 

2.  What  significance  has  the  presence  of  carbon  dioxide  gas  in  the  breath? 

3.  In  ventilating  rooms  and  buildings,  what  special  attention  must  be  given 

(a)  to  economic  considerations;  (b)  to  danger  to  health? 

4.  What  is  meant  by  a  flame?     Why  is  there  greater  danger  of  accident  in 
the  use  of  gasoline  than  of  kerosene? 

5.  State  some  ways  of  showing  that  the  interior  of  a  candle  flame  is  not  afire. 

6.  In  which  parts  of  plants  is  carbon  dioxide  gas  changed  chemically  into 

material  for  plant  structure  and  nourishment?     What  relation  to  this 
change  has  sunlight? 

7.  Why  is  there  need  to  give  less  attention  ordinarily  to  the  ventilation  of 
living  rooms  by  day  than  by  night?     Why  is  there  need  of  more  attention 
in  winter  than  in  summer? 

8.  In  tuberculosis  of  the  lungs  what  at  present  is  the  only  hopeful  course  of 

treatment?    When  only  is  this  successful?     What  conditions  in  living  are 
conducive  to  this  ailment? 

9.  About  what  on  an  average  is  (a)  the  rate  of  respiration;  (£>)  the  capacity 
of  the  lungs;  (c)  the  per  cent  of  the  lung  capacity  employed  at  a  breath? 

10.  What  advantages  (a)  in  the  gradual  change  of  the  air  in  the  lungs;  (b) 
in  the  retention  in  them  at  all  times  of  considerable  air? 

11.  What  good  purpose  is  served  by  habitual  deep  breathing?     What  are  the 
ill  effects  from  habitually  failing  to  inflate  the  lungs  fully  at  every  breath? 

12.  Describe  the  steps  to  be  taken  for  the  resuscitation  of  a  drowned  person. 
Give  the  reason  for  each  step. 

13.  What  is  the  apparent  relation  between  vigorous  exercise  whether  as  work 
or  play,  rapidity  of  breathing  and  of  heart  action,  and  the  temperature  of 
the  body? 

14.  In  what  sense  does  perspiration  "regulate"  the  temperature  of  the  body? 

15.  What  is  the  meaning  of  the  terms  {a)  congestion;  (b)  inflammation? 

16.  Why  is  there  risk  to  one's  health  from  damp  feet  or  clothing  when  not 
exercising? 

17.  What  relation  apparently  exists  between  temperature  maintained  in  the 
body  and  the  continuance  of  life  activities?     Explain  this. 

18.  What  is  the  purpose  (a)  of  the  digestion  of  food;  (b)  of  the  oxidation  of 

portions  of  it? 


III.  HEALTH  AND  WELL-BEING 

KEEPING  WELL 

Our  control  over  our  health  is  much  like  that  exercised 
by  gardeners  and  florists  over  the  growth  of  their  plants. 
Neglect  or  improper  care  is  ruinous  in  either  case.  Health 
and  disease  are  essentially  conditions  of  the  cells  of  the  body, 
and  of  the  fluids  about  the  cells.  Our  mastery  of  health  lies 
in  maintaining  the  right  conditions. 

A  knowledge  of  " nature's  laws"  is  of  little  purpose  unless 
our  manner  of  life  is  made  to  accord  with  them.  Our  un- 
willingness to  do  what  must  be  done  in  order  to  promote  and 
to  maintain  health  will  not  protect  us  from  the  consequences 
of  not  working  in  harmony  with  nature's  ways.  That  people 
who  have  reached  manhood  and  womanhood  in  a  vigorous 
state  of  health  do  not  maintain  their  health  and  efficiency 
to  eighty  years  and  upward  is  due  generally  to  wrong  ways 
in  living.  Many  of  the  diseases  proving  fatal  to  men  and 
women  in  the  prime  of  life  could  have  been  prevented  if 
these  persons  had  been  examined  periodically  by  a  competent 
physician,  and  had  followed  his  advice  as  to  diet,  sleep,  and 
exercise. 

Through  the  nervous  system  all  activities  of  the  body  are 
directed  and  harmonized.  Good  health  is  impossible  when 
the  cells  of  the  nervous  system  are  exhausted.  It  is  to  be 
remembered,  too,  that  the  bodily  energy  is  limited  in  quantity, 
and  that  what  is  expended  in  physical  exercise  is  not  avail- 
able for  mental  effort.  Undue  expenditures  for  either  or 
both  of  these  may  rob  the  organs  of  the  body  of  the  energy 
necessary  for  their  activities.  On  an  average  two  hours  a 

31 


32  GENERAL  SCIENCE 

day  or  more  of  suitable  exercise  is  a  minimum  requisite  for 
attaining  and  maintaining  a  high  state  of  bodily  health 
and  vigor.  Continued  neglect  of  exercise  is  likely  to  result 
in  an  unhealthful  state  of  the  body,  and  a  diminished  effi- 
ciency. Physical  exercise  should  be  as  congenial  to  persons 
living  a  normal  life  as  play  is  to  children.  Persons  suf- 
fering from  inability  to  sleep  often  find  in  manual  labor,  in 
long  walks  before  going  to  bed,  and  in  active  sports,  a  degree 
of  physical  exhaustion  that  is  conducive  to  sleep. 

To  one  who  is  at  all  thoughtful  it  is  a  marvel  how  lightly 
many  people  regard  health,  and  the  freedom  and  happiness 
that  depend  upon  it.  To  be  well  born,  and  to  have  the  con- 
ditions favorable  for  making  the  most  of  one's  life,  may  be 
considered  an  inalienable  right.  To  forfeit  good  health  and 
well-being  through  lack  of  enlightenment,  or  of  self  control, 
does  not  lessen  the  irreparable  loss  sustained  when  strength 
and  vigor  have  been  thrown  away,  and  life's  opportunities 
that  wait  upon  these  have  been  wasted. 

Sickness  usually  causes  more  or  less  of  pain,  and  life  it- 
self is  often  put  in  jeopardy.  A  sick  person  in  seeking  to 
regain  health  must  forego  the  usual  activities  of  life,  and  be 
subject  to  losses  through  inability  to  earn  and  as  expenditures 
incident  to  sickness.  Sickness  imposes  more  or  less  of  a  bur- 
den upon  those  who  are  called  upon  to  care  for  the  patient 
during  his  illness.  Many  times  ailments  supposed  to  have 
been  " inherited"  are  but  the  results  of  the  same  manner  of 
home  life  that  caused  impaired  health  in  the  parents.  At 
any  rate  it  is  a  great  mistake  ever  to  cease  making  intelli- 
gent efforts  so  to  regulate  one's  manner  of  life  as  to  overcome 
by  hygienic  living  all  defects  and  weaknesses  whether  in- 
herited or  not. 

Disease  and  serious  illness  ought  to  be  the  exception  rather 
than  a  common  condition.  In  adults  it  is  often  an  evidence 
of  a  failure  to  apply  ordinary  intelligence  to  the  care  of  the 


HEALTH  AND  WELL-BEING  33. 

health.  To  strive  to  maintain  the  highest  state  ol  health 
and  efficiency  in  life  is  not  only  a  wise  course,  but  it  is  due 
recognition  of  an  obligation  to  the  interests  of  those  in  one's 
own  family  and  in  the  community. 

Any  excessive  irritation  of  a  nerve,  whether  by  causes 
within  the  body  or  outside  of  it,  results  in  pain.  The  mind 
locates  the  cause  of  the  trouble  in  that  part  of  the  body 
where  the  particular  nerve  affected  is  distributed.  Pain 
in  any  part  of  the  body  may  be  considered  as  nature's 
warning  of  something  wrong  there,  and  a  call  of  distress 
from  that  part.  Without  the  nerve  to  give  this  warning, 
the  mind  would  have  no  knowledge  of  the  danger. 

But  so  interlaced  are  the  various  nerve  terminals,  and  so 
slowly  is  the  power  of  interpreting  sensations  acquired,  that 
oftentimes  the  one  who  is  suffering  may  be  entirely  wrong 
as  to  the  place  and  cause  of  the  ailment.  Even  the  trained 
and  experienced  physician  is  at  times  baffled  in  his  attempts 
to  diagnose  a  case  correctly.  Any  intelligent  treatment 
of  one  who  is  ill  is  out  of  question  until  the  cause  of  the 
ailment  is  known.  The  skilled  physician  seeks  to  restore  con- 
ditions in  the  body  of  the  patient  favorable  for  those  bodily 
processes  necessary  to  health. 

A  watch,  however  perfect  it  may  be  in  its  workmanship, 
is  of  little  value  as  a  time-piece  when  any  one  of  its  train 
of  wheels  is  improperly  adjusted  and  does  not  move  harmoni- 
ously with  the  others.  No  one  part  of  the  body  can  fail 
in  performing  its  function  (its  particular  work)  without 
harm  to  the  body  as  a  whole.  These  failures  may  result 
from  causes  external  to  the  body.  A  cinder  "in  the  eye," 
a  bit  of  food  lodged  in  the  larynx,  an  infected  sliver  under 
the  finger  nail,  may  cause  derangements  in  the  workings 
of  the  body  as  a  machine  even  as  a  bit  of  dust  when  in  the 
wheel-work  of  a  watch.  Medicines  are  given  as  an  aid  in 
restoring  natural  conditions  in  the  body.  In  cases  where 


34 


GENERAL  SCIENCE 


the   suffering   is   extreme    remedies   may    be   administered 
solely  to  ease  pain  and  conserve  the  strength  of  the  patient. 
In  all  muscular  tissues  the  arteries,  veins,  and  capillaries 
blende    in  a  perfect  network  of   blood   vessels.     Through 
them  the  blood  must  be  kept  moving  in  its  round  of  circula- 
tion so  that  the  tissues  may  be  properly  nourished.     The 
blood  is  being  continuously  purified  as  it 
passes  through  the  lungs  and  kidneys  and 
other    excretory    organs.      In   the   veins 
there  is  especial  need  to  urge  the  blood  on 
in  order  to  lighten  the  -effort  put  forth  by 
the  heart  in  forcing  along  a  sluggish  cir- 
culation.    The   " blood   pressure"    which 
the  heart  must  maintain  to  keep  the  flow 
of  blood  sufficiently  rapid  may  overwork 
and  weaken    it.      There    is    a    constant 
menace    of  rupturing    the    walls    of    the 
arteries  or  other  blood  vessels  under  any 
abnormal  pressure. 

In  the  veins  the  lining  in  places  is  so 
arranged    in    folds  as  to    form    pockets. 
These  allow   the   venous    blood    to   pass 
on  toward   the  heart  freely  enough,  but 
any  backward  flow  is  prevented   as    the 
veins   are   compressed  by  muscular   con- 
tractions.     Thus    it    is    that    muscular 
activities   result  in   a  better    circulation. 
This  brings  more  nourishment   to  the  muscles  themselves, 
and  maintains  a  better  state  of  the  whole  body. 

In  a  rush  of  blood  to  an  affected  part  of  the  body  to 
protect  it  from  harm,  and  to  repair  any  damage  already  done, 
there  is  occasionally  a  congested  state  of  the  blood  vessels 
of  that  particular  part.  This  is  seen  in  the  blood-shot 
appearance  of  the  eyeball,  and  the  feverish  condition  of 


FIG.  13.— Pocket- 
like  folds  in  the  lining 
of  veins  serve  as 
valves  to  prevent  in 
part  any  backward 
flow  of  blood. 
(Bundy.) 


HEALTH  AND  WELL-BEING  35 

the  tissues  about  it,  when  a  bit  of  dirt  gets  under  the  eyelid. 
One  of  the  means  commonly  employed  to  determine  whether 
the  body  as  a  whole  is  in  a  disturbed  and  unnatural  state 
is  by  " taking  the  temperature"  of  the  body.  Any  con- 
siderable departure  of  the  body  temperature  from  normal 
is  cause  for  concern.  Usually,  if  the  temperature  is  approxi- 
mately normal,  any  illness  experienced  is  likely  to  prove  a 
temporary  rather  than  a  serious  disturbance  of  the  bodily 
functions. 

The  small  tube  of  the  clinical  (klin'-I-kal)  thermometer 
used  by  physicians  is  very  much  narrowed  and  almost  closed 
just  above  the  bulb.  The  mercury  in  the  bulb  when  warmed 
is  crowded  up  through  this  narrow  opening,  and  can  be 
made  to  return  only  by  jarring  the  tube.  Since  the  mercury 
reading  is  always  the  highest  point  (temperature)  reached, 
the  instrument  is  one  form  of  a  maximum  thermometer. 

SUMMARY 

Sickness  and  health  are  conditions  of  the  body.  To  regain  health 
after  having  been  sick  necessitates  the  restoration  of  the  bodily  condi- 
tions upon  which  health  depends.  Medicines  are  only  an  aid  in  bring- 
ing this  about.  The  bodily  processes  alone  can  restore  impaired  health. 

Pain  is  nature's  warning  that  something  is  wrong  in  the  affected 
part  of  the  body,  and  it  may  be  considered  a  call  not  only  of  distress 
but  for  relief.  In  the  body  as  in  the  care  of  machinery  inattention  to 
parts  Out  of  adjustment  may  ruin  the  mechanism.  The  removal  of 
the  cause  of  an  ailment  constitutes  the  only  hope  of  keeping  the  body 
well  and  fit  to  do  its  work.  No  intelligent  treatment  of  one  who  is  ill 
is  possible  without  knowledge  of  the  cause  of  the  illness. 

Good  health  should  be  the  rule,  and  sickness  the  exception,  in  well 
regulated  living.  Intelligent  efforts  to  avoid  whatever  harms  the 
body,  and  wisely  to  direct  one's  manner  of  living,  is  ordinarily  the 
price  that  must  be  paid  for  good  health  and  long  life. 

There  are  times  when  the  harm  from  use  of  medicines  to  deaden 
pain  and  give  relief  from  suffering  is  less  than  the  exhaustion  from 
enduring  the  pain.  It  should  be  fully  understood,  however,  that  such 
relief  is  temporary,  and  is  not  in  any  sense  a  cure  of  the  ailment.  So 


36  GENERAL  SCIENCE 

dangerous  are  the  drugs  used  for  the  relief  of  pain,  and  so  ruinous  their 
long  continued  use,  that  under  no  conditions  are  they  to  be  employed 
save  by  direction  of  a  physician. 

Exercise  is  indispensable  to  the  maintenance  of  health  and  the 
development  of  the  body.  In  order  to  be  healthy  all  organs  must  be 
kept  active.  This  is  as  true  of  the  brain  as  of  other  parts  of  the  body. 
Labor  is  the  price  for  developing  and  maintaining  a  state  of  health. 
Work  becomes  a  curse  only  when  its  demands  on  time  and  strength 
are  excessive,  and  when  one  is  a  slave  to  it  rather  than  its  master. 


INFECTION 

Bacteriology,  or  the  study  of  microscopic  forms  of  life, 
is  a  new  science.  The  story  of  its  discoveries,  and  of  the 
benefits  which  already  have  come  to  mankind  through  it, 
is  as  fascinating  as  fiction.  Much  of  the  present  day 
knowledge  of  the  effects  of  living  organ'sms  of  microscopic 
size,  whether  one-celled  animals  known  as  protozoa  or  one- 
celled  plants  known  as  bacteria  (see  page  324),  dates  from  the 
researches  of  Louis  Pasteur  (1822-1895). 

In  1857  the  discovery  was  made  by  Pasteur  (pas'-tur) 
that  fermentation  is  due  to  the  action  of  bacteria.  In  1886 
he  was  successful  in  his  efforts  to  destroy  the  bacteria  infest- 
ing the  silk  worms  of  France  and  Italy  and  threatening  the 
destruction  of  the  silk  industry  there.  But  it  was  when 
he  turned  his  attention  to  the  study  of  the  causes  of  those 
diseases  transmitted  from  one  animal  to  another  that  the 
field  of  medical  bacteriology  was  opened  up. 

Some  of  his  first  experiments  were  with  chickens  affected 
by  cholera,  and  later  with  cattle  having  splenic  (splen'-ik) 
fever.  He  was  able  so  to  reduce  the  poisonous  effects  of  a 
virus  (poison)  containing  the  germs  of  a  disease  that  when 
it  was  administered  to  a  healthy  animal  only  a  mild  form 
of  the  disease  resulted,  and  the  animal  became  for  a  time 
immune  to  that  disease.  Here  was  the  beginning  of  the  use 


HEALTH  AND  WELL-BEING 


37 


of  serums  and  antitoxins,  and  an  explanation  of  the  immunity 
from  small  pox  by  vaccination  advocated  by  Dr.  Edward 
Jenner  (1749-1823)  and  practised  more  or  less  since  1796. 


FIG.   14. — Louis  Pasteur.     (From  Tower,  Smith  &  Turlon.) 

Notable  progress  has  been  made  in  the  prevention  of 
typhoid  by  vaccination.  It  already  seems  probable  that 
like  small  pox  it  is  one  of  the  dread  diseases  that  will  always 
be  under  control,  and  in  time  largely  disappear.  The 
vaccine  material  used  contains  dead  typhoid  germs  that 
have  been  grown  outside  the  body  and  then  killed.  Usually 


38  GENERAL  SCIENCE 

three  injections  are  given  ten  days  apart,  and  as  a  rule  no 
interference  with  one's  daily  duties  is  experienced  from  the 
vaccination.  Cases  of  typhoid  are  already  rare  occurrences 
in  military  camps  because  of  enforced  vaccination,  and  a 
strict  observance  of  sanitary  regulations.  Discharges  from 
the  bowels  and  kidneys  of  typhoid  patients  should  always 
be  treated  with  a  strong  solution  of  "chloride  of  lime"  for 
twenty  minutes  or  more  to  destroy  the  germs  before  being 
thrown  into  cesspool  or  sewer.  The  danger  of  spreading 
the  disease  is  thus  greatly  lessened. 

An  understanding  of  the  nature  of  many  of  the  most 
terrible  germ  diseases  that  afflict  humanity  is  one  of  the 
notable  achievements  of  the  years  just  at  the  close  of  the 
nineteenth  century  and  at  the  beginning  of  the  twentieth. 
There  is  reason  to  believe  that  the  time  may  come  when 
their  ravages  will  cease  to  be  the  scourge  of  humanity. 
Preventive  measures  combined  with  medical  skill  and 
enforced  sanitation  have  already  accomplished  much  toward 
this  end. 

Malaria,  the  sleeping  sickness  of  Africa,  and  splenic 
fever  in  cattle  are  due  to  protozoa.  The  list  attributed  to 
bacteria  includes  typhoid,  tuberculosis,  pneumonia,  tetanus 
(lockjaw),  meningitis,  influenza  (grippe),  diphtheria,  leprosy, 
cholera,  and  bubonic  plague.  Measles,  hydrophobia, 
scarlet  fever,  small  pox,  whooping-cough,  and  yellow  fever 
are  other  infectious  diseases  not  so  positively  classified. 
To  this  list  may  doubtless  be  added  the  dread  diseases  of 
cancer  and  infantile  paralysis. 

Many  of  the  so-called  " children's  diseases,"  such  as 
measles,  scarlet  fever,  and  whooping-cough,  are  not  only 
to  be  avoided  but  should  be  regarded  as  highly  dangerous. 
This  is  chiefly  on  account  of  possible  complications  with 
other  diseases,  and  because  of  a  train  of  serious  lifelong 
ailments  that  follow  them,  such  as  weakened  eyes,  affected 


HEALTH  AND  WELL-BEING  39 

ears,  and  a  condition  of  throat  and  lungs  that  makes  them 
highly  susceptible  to  germ  diseases. 

The  extended  use  of  antiseptics  to  prevent  infection  of 
wounds,  is  associated  with  the  name  of  one  of  Pasteur's 
pupils,  Sir  Joseph  Lister  (1827-1912),  the  famous  English 
surgeon.  The  Pasteur  Institute  in  Paris,  and  others  of  its 
kind  elsewhere  in  the  world,  have  been  established  for  the 
purpose  of  giving  treatment  for  rabies  based  on  the  dis- 
coveries of  Pasteur  concerning  hydrophobia  (1885).  In< 


FIG.   15. — Robert  Koch. 

1882  the  German  scientist  Robert  Koch  (kok)  discovered 
the  germ  of  tuberculosis,  and  in  1883  the  germ  of  Asiatic 
cholera.  Von  Behring,  a  German  bacteriologist,  discovered 
an  antitoxin  for  diphtheria  in  1892. 

It  was  during  the  occupation  of  Cuba  by  the  forces  of  the 
United  States  (1900)  that  the  part  played  in  the  spread  of 
yellow  fever  by  one  kind  of  mosquito  (Steg-o'-mi-a)  was 
definitely  established.  By  reason  of  the  preventive  measures 
taken,  that  scourge  of  the  Tropics  was  soon  almost  com- 


40  GENERAL  SCIENCE 

pletely  eliminated  from  the  death  lists  of  Havana.  So 
marked  has  the  control  of  germ  diseases  become  in  the  pres- 
ent generation  that  during  the  building  of  the  Panama 
Canal  (completed  in  1914)  the  health  record  there  under 
American  management  was  better  than  in  many%cities  of 
the  United  States.  Under  French  management  of  the  canal 
in  the  earlier  years,  and  likewise  when  the  Panama  Railroad 
was  built,  the  death  lists  numbered  thousands1. 

Bacteria  and  protozoa  that  exist  in  or  upon  living  plants 
or  animals  are  known  as  parasites.  Those  that  live  upon 
dead  or  decaying  organic  matter  are  called  saprophites 
(sap'ro-fits).  As  result  of  the  growth  and  multiplication 
of  these  micro-organisms  the  tissues  upon  which  they  feed 
are  broken  down.  In  the  human  system  the  waste  products 
of  their  activities  seem  to  act  as  poisons  (toxins),  destroying 
the  protoplasm  of  the  cells.  The  expenditure  of  bodily 
energy  on  the  part  of  living  tissues  in  a  battle  against  these 
destructive  agencies,  and  in  the  elimination  of  the  excessive 
wastes  of  the  body,  is  indicated  in  a  fevered  state  of  the 
patient. 

The  body  after  having  become  infected  seems  to  have  the 
power  to  produce  products  known  as  antitoxins.  These 
either  neutralize  the  effects  of  the  toxins,  or  stop  the  mul- 
tiplication of  the  disease  germs,  or  both.  If  these  anti- 
toxins are  produced  rapidly  enough  after  a  person  is  infected, 
and  in  sufficient  quantity,  the  patient  recovers  even  from 
the  most  severe  attacks;  if  not,  he  is  likely  to  die.  At 
times  a  patient  surviving  the  cycle  of  life  changes  of  the 
first  of  the  germs  has  a  "  relapse,"  and  a  recurrence  of  the 
disease  but  with  the  original  symptoms  less  pronounced. 

1  The  annual  death  rate  of  employees  of  the  French  company  (1882-1890) 
was  reported  to  be  231  per  thousand.  Under  the  later  American  control, 
when  the  agency  of  mosquitoes  in  yellow  fever  and  malaria  had  become 
known,  the  death  rate  was  reduced  to  17  per  thousand.  There  were  no  cases 
of  yellow  fever  from  1906  to  1911. 


HEALTH  AND  WELL-BEING  41 

Though  at  such  times  in  a  much  weakened  state  by  reason 
of  the  period  of  sickness  that  has  preceded,  the  patient  may 
recover.  The  poisonous  waste  products  of  bacteria  in  the 
putrefaction  of  foods  are  known  as  ptomaines  (to-ma-inz). 

The  efficacy  of  serums  as  prepared  from  the  blood  of 
animals  known  to  have  had  an  infectious  disease  seems  to 
lie  in  the  fact  that  such  blood  contains  antitoxins  of  the 
disease.  A  person  inoculated  with  this  serum  is  thus  fur- 
nished protection  against  toxins  developed  in  his  own  system 
by  the  multiplication  of  germs.  Serious  illness  or  death 
is  thus  prevented  during  the  time  needed  for  his  own  body 
to  produce  the  antitoxins  in  sufficient  quantity. 

The  toxins  left  in  the  blood  by  a  disease  often  prove 
harmful  to  organs  that  have,  not  been  infected,  and  death 
may  result  from  it  indirectly  as  in  case  of  heart  failure  follow- 
ing pneumonia. 

Children  often  have  diphtheria  germs  in  the  throat  for 
some  considerable  time  after  their  recovery  from  the  disease. 
They  may  spread  the  diphtheria  if  allowed  to  return  to 
school  before  a  microscopic  examination  of  discharges  from 
the  throat  by  a  physician  has  shown  it  free  of  the  germs. 
The  diphtheria  serum,  first  prepared  by  Von  Behring,  is 
from  the  blood  of  a  horse.  It  contains  the  antitoxins  of 
diphtheria  developed  in  the  animal  during  a  prolonged 
period  of  infection.  When  diphtheria  antitoxin  is  used  at 
the  first  symptoms  of  the  disease  few  deaths  occur,  while 
otherwise  it  is  often  fatal. 

The  simple  direction  that  the  fingers  and  objects  generally 
must  not  be  put  into  the  mouth  should  be  insisted  upon  with 
children  after  the  period  of  infancy  till  its  observance  has 
become  habitual.  The  hands  should  always  be  washed  before 
eating  as  a  protection  against  infection  as  well  as  for  personal 
cleanliness.  Fruits  such  as  apples,  peaches,  grapes,  berries, 
etc.,,  and  all  garden  stuff  that  is  eaten  uncooked,  such  as 


42  GENERAL  SCIENCE 

celery  and  cabbage,  should  be  washed  until  any  danger  of 
disease  germs  from  the  soil,  the  air,  or  from  dust  is  unlikely. 
It  seems  wholly  reasonable  to  believe  the  statements  that 
more  than  one-half  the  sickness,  and  of  the  wretchedness 
caused  by  sickness,  is  produced  by  disease  germs.  Much  of 
this  terrible  waste  can  be  avoided  by  enlightened  action 
on  the  part  of  individuals  and  communities.  Many  of  the 
worst  diseases  that  afflict  mankind  would  speedily  be  brought 


FIG.   1 6. — Danger  of  infection.     Why  not  walk? 

under  control,  and  perhaps  would  disappear,  if  the  scattering 
of  disease  germs  through  carelessness  and  ignorance  could 
be  prevented.  It  is  to  be  remembered  always  that  disease 
germs  come  from  sick  people  or  sick  animals,  and  that  to  pre- 
vent the  dissemination  of  these  germs  is  to  wipe  out  the 
disease. 

Instruction  in  schools  has  an  important  part  in  this 
warfare  upon  disease.  Attention  to  one's  own  health 
as  result  of  studies  in  hygiene,  and  care  given  the  health 


HEALTH  AND  WELL-BEING  43 

conditions  of  a  community  through  wise  sanitary  regula- 
tions, are  matters  of  utmost  importance.  However,  even 
the  healthiest  person  has  times  of  physical  weariness,  depres- 
sion, and  weakness.  At  such  times  germs  already  within 
the  body  may  get  beyond  control. 

Physicians  are  required  by  law  to  report  at  once  to  the 
Board  of  Health  all  cases  of  contagious  disease.  The 
place  where  any  such  disease  exists  is  at  once  quarantined. 
A  placard  is  posted  giving  warning  of  the  disease,  and 
forbidding  persons  to  enter  or  leave  the  building.  Germs 
of  many  diseases  may  be  carried  on  the  person  or  in  the  cloth- 
ing of  those  who  have  come  in  contact  with  an  infected 
person.  All  members  of  a  family  where  there  is  a  contagious 
disease  must  be  made  either  to  remain  at  home  or  to  keep 
away  from  home  in  order  to  lessen  the  likelihood  of  the 
spread  of  the  disease. 

The  quarantine  period  varies  according  to  the  length  of 
time  within  which  serious  danger  of  infection  exists.  Before 
the  quarantine  of  a  room  or  building  is  removed  it  must  be 
thoroughly  disinfected  under  the  direction  of  the  Board  of 
Health.  It  is  the  duty  of  every  person  faithfully  to  obey 
the  quarantine  regulations,  however  irksome  these  may 
seem,  because  of  the  need  to  safeguard  the  health  and  the 
lives  of  others. 

Ships  coming  into  harbor  are  often  held  in  quarantine 
when  cases  of  contagious  disease  have  occurred  during  the 
voyage,  and  neither  people  nor  cargo  allowed  to  land  till 
properly  disinfected.  A  quarantine  is  at  times  placed  upon 
cattle  and  horses  within  certain  districts  where  contagious 
diseases  affecting  them  have  become  epidemic. 

The  use  of  formalin  (formaldehyde  gas  in  solution)  proves 
a  satisfactory  disinfectant  for  rooms  and  buildings.  The 
furniture  should  be  left  in  the  room,  and  the  bedding,  rugs, 
and  all  clothing  should  be  so  spread  out  and  hung  up  that 


GENERAL  SCIENCE 


the  disinfecting  gas  can  get  into  every  part  of  them.  All 
cracks  and  openings  of  the  room  should  be  stopped  gas 
tight.  About  a  pint  of  the  40  per  cent  solution  serves  for  a 
room  of  ordinary  size,  and  the  room  should  be  kept  tightly 
closed  for  twenty-four  hours.  Where  sulphur  is  left  burning 
in  the  closed  room  there  is  always  more  or  less  danger  of 
fire,  and  the  disinfection  from  sulphur 
alone  is  less  satisfactory. 

It  needs  to  be  emphasized  that  most 
kinds  of  bacteria  are  harmless  to  man, 
and  many  kinds  are  of  the  greatest  im- 
portance to  his  well-being.  On  the 
roots  of  such  plants  as  peas,  beans, 
clover,  and  alfalfa,  certain  bacteria 
thrive  that  have  the  power  to  abstract 
nitrogen  from  the  atmosphere  and 
convert  it  into  compounds.  These 
nitrogen  compounds  later  serve  as 
plant  food,  thus  increasing  the  fertility 
of  the  soil.  Other  bacteria  give  to 
butter  and  cheese  their  appetizing 
By  the  multiplication  of  certain  bac- 
teria in  sewage  it  is  rendered  harmless.  If  it  were  not 
for  the  action  of  bacteria  concerned  in  the  decay  of  organic 
matter,  the  collection  of  refuse  material  in  thickly  settled 
sections  would  constitute  an  ever  growing  problem. 
Carbon  taken  from  the  carbon  dioxide  of  the  air,  and  nitrogen 
from  soluble  material  as  plant  food  in  the  soil,  would  thus, 
rapidly  become  accumulated  in  dead  organic  bodies,  and 
be  unavailable  for  plant  growth. 

SUMMARY 

With  the  use  of  the  term  infection  is  associated  the  idea  of  disease 
transmitted  by  germs.  These  germs  are  microscopic  one-celled  plants 
known  as  bacteria,  or  are  one-celled  animals  known  as  protozoa.  In 


FIG.  17. — The  homes 
of  "nitrogen -  fi  xi  ng" 
bacteria.  (Conn.) 

tastes   and   odors. 


HEALTH  AND  WELL-BEING  45 

both  cases  they  are  parasites,  and  they  are  destructive  of  the  tissues 
in  which  they  lodge  and  multiply. 

As  the  germs  live  and  multiply  they  also  produce  substances  known 
as  toxins  which  have  the  effect  of  poisons  upon  the  body  as  a  whole. 
The  human  body  when  infected  seems  to  have  the  power  of  forming 
other  substances  known  as  antitoxins  which  counteract  the  effects  of 
the  toxins.  If  these  are  in  sufficient  quantity  in  the  body  they  lessen 
the  severity  of  the  illness  or  wholly  prevent  its  development. 

Blood  withdrawn  from  an  animal  which  has  had  an  infectious  dis- 
ease, such  as  diphtheria,  is  supposed  to  contain  in  its  watery  part,  or 
serum,  antitoxins  developed  in  the  animal.  This  serum  introduced 
into  the  blood  of  a  human  being  counteracts  the  poisonous  effects  of 
the  germ  life  without  waiting  for  the  slow  development  of  antitoxins  in 
the  body  of  the  one  who  is  ill. 

Hope  of  controlling  infectious  diseases,  if  not  of  their  eradication, 
lies  in  the  prevention  of  the  scattering  of  the  germs  developed  in  in- 
fected persons.  This  involves  the  isolation  by  quarantine  or  otherwise 
of  any  one  sick  with  an  infectious  disease.  It  is  equally  important  that 
all  discharges  from  the  body  of  the  patient,  and  all  infected  clothing  and 
other  articles,  shall  be  disinfected  thoroughly  by  use  of  chemicals,  by 
sterilization,  or  by  fumigation.  The  discharges  from  bowels  and  kid- 
neys especially  should  be  treated  with  a  strong  solution  of  hypochlorite 
("chloride")  of  lime  before  being  thrown  into  sewer  or  cesspool. 

Danger  of  infection  through  foodstuffs  is  almost  wholly  removed  by 
thorough  cooking.  In  the  laundry  clothing  should  be  boiled  for  fifteen 
or  twenty  minutes.  Raw  vegetables  and  fruits,  and  milk  not  pasteur- 
ized, are  always  possible  means  of  infection.  One  argument  for  the 
use  of  hot  drinks  rather  than  cold  water  lies  in  the  use  of  water  that 
has  been  boiled. 

SANITATION 

Providing  the  food -supply  for  a  family  to-day  in  the 
United  States  is  a  very  different  matter  from  what  it  was  a 
half  century  ago.  Then  the  vegetables,  fruits,  and  meats, 
together  with  the  products  of  poultry  yard  and  dairy,  were 
home  products  for  home  consumption,  or  were  bought 
direct  from  the  producer.  Home-grown  animals  were 
slaughtered  at  home.  Some  of  the  meat  was  used  fresh, 


46 


GENERAL  SCIENCE 


and  other  portions  cured  at  home  for  later  use  by  salting, 
pickling,  smoking,  and  drying.  Cellars  and  caves  were 
piled  with  potatoes  and  other  vegetables,  together  with 
apples  and  other  orchard  products.  The  rafters  were  hung 
with  dried  fruits,  while  pickles  and  preserves  added  variety 
in  diet.  Fresh  eggs,  with  plenty  of  milk  and  poultry  always 
at  hand,  made  necessary  but  few  food  supplies  from  town. 


FIG.   1 8. — Insanitary  conditions  here. 

Not  infrequently  there  was  on  hand  enough  food  to  last 
through  the  months  of  a  winter  season. 

To-day  the  grocer,  butcher,  baker,  and  milkman  furnish 
the  family  supplies  as  needed  day  by  day.  Who  selects 
and  prepares  these  foodstuffs,  and  whether  or  not  it  rs  done 
under  sanitary  conditions,  is  unknown  to  the  purchaser. 
It  thus  becomes  necessary  as  a  matter  of  self-protection  to 
enact  stringent  laws  governing  the  preparation  and  the 
quality  of  the  food  supplies  put  on  the  market.  Provision 


HEALTH  AND  WELL-BEING  47 

must  be  made  for  food  inspectors  as  public  officials  to  see  to 
it  that  these  laws  and  their  penalties  are  enforced.  An 
enlightened  citizenship  is  necessary  that  these  officials  may 
have  an  active  support  and  a  hearty  co-operation  in  law 
enforcement.  Those  desirous  of  carrying  on  business  in  an 
honest  and  law-abiding  manner  should  not  be  compelled 
to  meet  the  competition  of  those  who  by  misbranding,  adul- 
teration, short  weights,  and  other  fraudulent  practices  seek 
unfair  advantage  at  the  expense  of  purchasers. 

Preservatives  are  sometimes  used  in  foodstuffs  to  prevent 
chemical  changes  caused  by  bacteria.  Milk  can  then  be 
kept  a  longer  time  from  becoming  sour,  and  meat  from 
becoming  tainted.  Some  preservatives  are  prohibited  by 
law  because  it  is  believed  they  interfere  with  the  chemical 
changes  involved  in  the  digestion  of  the  preserved  foods,  or 
because  they  act  injuriously  upon  the  tissues  of  the  body. 
Small  amounts  of  preservatives  are  at  times  used  in  foods 
put  up  in  cans  or  other  sealed  containers  when  the  food 
material  as  prepared  for  market  is  of  an  unwholesome  or 
inferior  character. 

Bacteria  multiply  in  summer  much  more  rapidly  than  in 
winter.  Fish  must  be  kept  continuously  on  ice  in  summer 
since  it  decays  rapidly  and  soon  becomes  dangerous  for  use. 
Meat  of  all  kinds,  including  fish,  and  poultry,  and  "shell- 
fish," soon  spoils  when  removed  from  cold  storage  or  from 
cans.  This  is  due  to  the  rapid  multiplication  of  bacteria  in 
it.  The  refreezing  of  melted  ice  cream  in  which  there  are 
any  poisonous  secretions  known  as  ptomaines,  developed 
from  bacteria  while  the  cream  was  unfrozen,  does  not  free 
it  from  its  dangerous  character  however  appetizing  it  is 
made  to  appear  by  use  of  flavors  and  coloring  material. 
Poisonous  products  from  bacteria  increase  rapidly  in  milk 
in  summer  time,  causing  wide  spread  illness  and  death  among 
babies.  Fresh  milk  and  other  fresh  foods  contain  no  pto- 


48  GENERAL  SCIENCE 

maines.  Bacteria  develop  slowly  or  not  at  all  at  a  low  tem- 
perature, or  in  foods  preserved  in  sugar,  vinegar,  salt,  or  by 
use  of  smoke.  Meats  and  fruit  products,  such  as  catsup 
and  sausage,  left  exposed  for  sale  day  after  day  without  spoil- 
ing presumably  contain  chemicals  that  prevent  multiplica- 
tion of  bacteria.  These  chemicals  likewise  make  the  foods 
kss  digestible  if  not  positively  harmful. 

It  is  a  part  of  the  varied  duties  of  Food  Inspectors  to  see 
that  no  use  is  made  of  impure  and  unwholesome  material  in 
the  preparation  of  foodstuffs,  however  attractive  these  may 


PIG.   19. — Typhoid  fever  germs  highly  magnified,  and  much  more  in  2  than 

in  i. 

be  made  in  appearance  and  price.  The  use  of  any  cheaper 
quality  of  a  substance,  or  of  a  cheaper  substitute  in  the 
preparation  of  a  staple  foodstuff,  constitutes  an  adulteration 
and  is  prohibited.  Any  dishonesty  in  sale  of  articles  under 
a  misleading  brand  or  label  is  in  violation  of  law.  The 
general  principle  involved  is  that  while  the  purchaser  has 
the  right  to  buy  whatever  he  pleases,  providing  it  is  not  an 
open  menace  to  health,  he  needs  protection  in  getting  what 
he  pays  for  so  far  as  its  nature,  quality,  and  quantity  are 
concerned.  The  various  States  by  laws  of  their  own,  and 
in  co-operation  with  the  national  government  through  its 
interstate  commerce  legislation,  seek  to  prevent  wholesale 
impairment  of  the  health  of  the  nation  through  its  food 
supply.  Upon  a  rigid  enforcement  of  pure  food  legislation, 
and  upon  the  skill  of  those  who  make  chemical  analyses  of 


HEALTH  AND  WELL-BEING  49 

foodstuffs  sold  in  the  open  market,  the  public  must  depend 
for  a  large  measure  of  its  protection  against  loss  in  efficiency 
and  shortened  lives  due  to  unfit  substances  in  the  foods 
purchased.  As  a  bacteriologist  the  sanitary  expert  must  be 
able  to  recognize  and  identify  any  disease  germs  present 
in  the  water,  milk,  and  food  supply  of  a  community. 

To  qualify  as  an  expert  in  any  one  science  usually  requires 
college  and  university  training.  But  so  simple  are  the  funda- 
mentals of  sanitation  that  the  sciences  of  the  high  school  give 
a  good  understanding  of  the  conditions  for  personal  and 
community  health,  and  how  these  may  be  conserved.  The 
relationships  and  applications  of  hygiene  and  sanitation  are 
as  wide  and  as  far  reaching  as  are  human  activities  and  inter- 
ests. No  one  in  a  family  circle  can  suffer  sickness  or  disease 
without  in  some  measure  affecting  the  interests  of  all  its 
members.  The  health  and  well-being  of  every  individual 
is  a  matter  of  concern  for  the  community  and  the  State. 

Directly  or  indirectly  those  now  in  the  public  schools  need 
to  be  concerned  with  the  safe-guarding  of  the  health  of  those 
who  work  in  factory,  shop,  mill,  store,  and  office.  In  later 
years  nearly  every  boy  and  girl  now  in  school,  either  as  em- 
ployers of  labor  or  as  employees,  will  have  a  personal  as 
well  as  an  industrial  and  social  interest  in  the  sanitary  condi- 
tions under  which  the  indoors  work  of  the  world  is  being 
carried  on.  Even  in  school  days  the  health  of  the  parents, 
whose  earnings  make  possible  the  maintenance  of  homes  and 
the  welfare  of  the  family,  are  matters  of  concern  to  all  boys 
and  girls. 

In  towns  having  a  good  supply  of  city  water,  with  modern 
plumbing  conditions,  there  is  absolutely  no  excuse  for  any 
lack  in  shops,  mills,  factories,  and  public  schools  of  sanitary 
drinking  fountains,  and  of  well-kept  toilet  rooms.  To  keep 
the  floors,  walls,  and  fixtures  of  toilet  rooms  neat  and  clean 
requires  co-operation  with  the  care-takers  of  the  buildings. 


SO  GENERAL  SCIENCE 

Misuse  of  these  rooms  and  of  their  furnishings  by  any  one  is 
evidence  of  unfitness  to  associate  with  those  whose  ways 
are  decent  and  considerate. 

The  extended  use  of  ice  in  summer  time,  especially  when 
put  into  water  or  other  drinks  to  cool  them,  involves  risks 
to  health  from  two  causes.  The  chilling  effect  upon  the 
digestive  tract,  due  to  any  reduction  in  temperature  much 


FIG.  20. — Sanitary  drinking  fountain. 

below  99°  F.  not  only  seriously  affects  the  distribution  of  the 
blood  supply  of  the  body  but  it  impairs  the  powers  of  secret- 
ing the  digestive  fluids.  Then,  too,  there  is  the  ever  present 
danger  of  infection  from  the  ice.  Whether  artificial  or 
natural,  it  may  have  become  contaminated  either  in  its 
storage  or  in  its  distribution  to  the  consumer.  Complete 
protection  from  infection  demands  that  ice  shall  never  be  put 
into  drinks  of  any  kind. 


HEALTH  AND  WELL-BEING  51 

SUMMARY 

Sanitary  regulations  and  pure  food  laws  in  late  years  have  become 
more  and  more  matters  of  importance.  There  is  need  of  the  strictest 
supervision  over  all  sources  of  the  food  supply,  and  over  the  manner  of 
preparation  and  sale  of  foods.  The  rigid  enforcement  of  all  regulations 
affecting  public  health  has  become  imperative. 

The  food  supply  of  a  family  to-day  is  very  largely  from  sources 
outside  the  home,  and  it  has  been  handled  by  persons  unknown.  The 
purchaser  cannot  be  expected  to  know  how  it  has  been  prepared  and 
cared  for.  Wholly  unfit  materials  may  have  been  put  up  in  an  attrac- 
tive form  for  sale;  chemicals  destructive  of  health  may  have  been  used; 
and  substances  of  inferior  quality  may  have  been  introduced  as 
adulterants. 

In  order  to  preserve  foods  for  long  periods  in  condition  fit  for  use, 
they  are  salted,  smoked,  preserved  in  sugar,  or  kept  at  or  below  freezing 
temperature.  All  these  conditions  hinder  the  multiplication  of  the 
germs  that  cause  decay  in  organic  matter.  Where  foodstuffs  are 
canned  the  materials  are  sterilized  at  a  high  temperature,  and  are  then 
sealed  air-tight  in  cans  to  prevent  the  entrance  of  germs. 

Ice  cream  that  has  been  allowed  to  melt  may  be  refrozen,  but  the 
refreezing  does  not  destroy  products  of  decay  in  it.  Serious  and  even 
fatal  results  as  ptomaine  posioning  may  follow  the  use  of  foods  con- 
taining the  products  of  decay. 

Instruction  in  the  schools  is  concerned  with  whatever  affects  the 
public  health  as  well  as  that  of  individuals.  It  should  contribute 
toward  an  enlightened  citizenship  that  will  enforce  laws  and  regula- 
tions for  the  welfare  of  community  life. 

Exercises 

1.  What  constitutes  being  temperate  in  one's  living? 

2.  Distinguish  between  bacteria  and  other  "microbes." 

3.  In  what  ways  does  the  multiplying  of  bacteria  (or  protozoa)  within  a 
person's  body  cause  sickness,  and  bring  about  a  diseased  state? 

4.  Account  for  the  certain  "periods"  through  which  different  diseases  run? 
What  may  be  the  explanation  of  a  relapse,  or  a  recurrence  of  the  same 
ailment  with  all  the  original  symptoms? 

6.  Give  general  definitions  of  (a)  virus;  (b)  serum;   (c)  vaccination;  (d) 
inoculation. 

6.  What  is  it  to  be  immune  to  any  disease?     How  is  immunity  explained? 

7.  What  is  an  antitoxin?     Explain  its  remedial  effects. 


52  GENERAL  SCIENCE 

8.  Distinguish  between  (a)  infectious  and  contagious  diseases;  (b]  antiseptic 
treatments  and  sterilization. 

9.  Wherein  lies  the  great  worth  of  formalin  as  a  disinfectant? 

10.  Of  the  various  disinfectants  whose  solutions  are  used,  which  is  perhaps 
the  most  generally  satisfactory  for  treatment  of  waste  material  from  sick 
rooms? 

11.  What  is  a  wise  course  in  the  matter  (a)  of  wearing  other  people's  clothing; 

(6)  of  using  public  drinking  cups  and  towels? 

12.  What  possible  dangers  are  there  in  the  use  of  public  plunge  baths  and 
swimming  pools? 

13.  What  sanitary  purpose  is  served  by  cooking  all  meats?     In  the  canning  of 
perishable  foodstuffs,  upon  what  does  their  preservation  depend? 

14.  How  is  a  case  of  any  contagious  disease  to  be  accounted  for  when  so  far 
as  known  the  patient  has  not  been  "exposed?" 

16.  About  how  many  years  is  it  since  Pasteur's  use  of  the  microscope  laid  the 
foundations  of  bacteriology?  Tell  something  of  his  early  discoveries. 
Mention  other  men  whose  researches  have  made  notable  advances  in  this 
field  of  science. 

16.  What  is  a  necessary  course  to  pursue  with  fruits  and  vegetables  from  the 

market  which  are  to  be  served  at  table  without  being  cooked?     Name 
several  fruits  and  vegetables  eaten  uncooked. 

17.  Under  what  conditions  might  ailments  ordinarily  not  quarantined,  such 
as  whooping-cough,  prove  serious  and  even  fatal? 

18.  What  are  the  usual  restrictions  placed  upon  people  when  quarantined? 

19.  Of  vaccination  for  the  prevention  of  typhoid  fever  tell  (a)  how  it.  is  done; 

(b)  what  the  vaccine  is. 

THE  WATER  SUPPLY  AND  HEALTH 

An  attempt  to  list  the  various  uses  of  water,  and  to  state 
the  part  that  it  plays  in  the  economy  of  nature  and  the  wel- 
fare of  men,  proves  highly  instructive.  The  extent  of  its 
uses  is  scarcely  more  striking  than  is  the  abundance  of  the 
supply  needed  for  these  uses.  The  round  of  changes  in  place 
and  form  undergone  by  water  in  the  economy  of  nature  is 
one  of  the  marvels  of  the  natural  world.  In  cities  provision 
must  be  made  to  furnish  water  for  drinking  purposes,  for 
cooking  foods,  for  use  as  steam  power  in  mills,  shops,  and 
factories,  and  for  heating  dwellings  and  other  buildings.  An 
enormous  supply  is  necessary  for  the  disposal  of  sewage,  for 
fire  protection,  for  laundry  and  bathroom,  for  lawn  and 


HEALTH  AND  WELL-BEING 


53 


garden,  and  as  ice  for  refrigeration.  Large  quantities  of 
water  are  necessary  in  factories,  gas  works,  dye  houses,  and 
other  industries.  It  is  indispensable  for  the  maintenance  of 
all  plant  and  animal  life,  and  for  human  existence. 

New  York  City  gets  a  portion  of  the  enormous  supply 
needed  by  its  population  and  for  its  varied  industries  from 
the  watershed  of  the  Catskill  Mountains  ninety  miles  away. 
The  expenditures  of  this  one  city  alone  for  its  supply  and 
distributing  systems  represents  outlays  of  hundreds  of 


FIG.  21. — Contamination    of    well    water.     (U.    S.    Public    Health   Service.) 

millions  of  dollars.  Transportation  by  water  has  in  all  ages 
been  one  of  the  chief  agencies  in  the  promotion  of  manufac- 
tures, of  commerce,  and  of  .civilization  itself. 

After  surface  waters  from  rainfall  and  melting  snows  have 
soaked  down  into  the  earth's  crust  any  considerable  number 
of  feet,  these  waters  commonly  may  be  considered  pure  by 
reason  of  filtration  and  aeration.  Slow  oxidation  will  have 
freed  the  water  of  organic  matter,  and  the  material  in  solu- 
tion will  be  harmless  minerals.  Drainage  from  barnyards, 
cesspools,  privies,  and  house  drains  may,  however,  find  its 


54 


GENERAL  SCIENCE 


way  into  the  waters  that  collect  in.  surf  ace  wells.  This  sew- 
age is  not  only  poisonous  to  the  system,  but  it  may  carry 
into  the  well  water  disease  germs  such  as  typhoid.  In  towns 
and  cities  where  soils  are  laden  with  organic  waste  material 
the  use  of  water  from  surface  wells  is  prohibited.  Unless  one 
knows  the  conditions  surrounding  a  surface  well,  and  some- 
thing of  the  strata  into  which 
it  was  dug,  it  is  always  wise 
to  regard  with  suspicion  any 
water  taken  from  it  for 
drink  or  for  use  in  preparing 
foods. 

Surface  waters  sometimes 
find  their  way  down  between 
layers  of  rock  that  are  sep- 
arated by  a  porous  stratum 
where  they  collect  under  the 
pressure  of  their  own  ac- 
cumulation. Boring  down 
into  this  water-filled  layer 
may  result  in  a  rise  of  these 
underground  waters  to  or 
above  the  surface  of  the 
ground.  Such-  waters  are 
usually  free  of  organic  matter 
and  disease  germs  by  natural 

filtration  and  aeration,  but  may  hold  much  mineral  matter 
in  solution. 

Where  rain  water  is  caught  and  stored  in  cisterns,  in  spite 
of  all  precautions  more  or  less  of  dust  and  of  decaying 
vegetable  matter  will  be  washed  from  the  roofs  into  the 
cisterns.  The  water  may  acquire  a  disagreeable  odor  and 
taste  from  the  decay  of  the  organic  matter  present,  and  be- 
come more  or  less  dangerous  as  a  drink.  This  organic 


FIG.  22. — Use  of  chain  pumps  to 
aerate  cistern  water.  The  inverted 
metal  cups  carry  air  down  into  the 
water  and  liberate  it  as  the  cups  fill 
with  water  at  the  bottom. 


HEALTH  AND  WELL-BEING 


55 


matter  may  be  destroyed  by  a  sufficient  supply  of  oxygen 
dissolved  in  the  water.  This  aeration  is  very  satisfactorily 
accomplished  by  use  of  a  pump  that  carries  water  up  on  one 
side  of  an  endless  chain  in  a  series  of  small  metal  cups 


FIG.  23. — An  air-pressure  water  system  and  plumbing  for  a  house  where 
there  is  no  city  water  supply.  The  pumping  may  be  done  by  hand,  by  a  gaso- 
line engine,  or  by  a  windmill. 

attached  to  the  chain.  This  chain  runs  over  two  wheels, 
one  at  the  surface  and  one  held  suspended  down  in  the  water 
near  the  bottom  of  the  cistern.  As  these  cups  are  inverted 
when  they  pass  down  into  the  water,  air  is  taken  down  and 


56  GENERAL  SCIENCE 

liberated  within  the  cistern  waters  every  time  the  pump  is 
used. 

There  is  always  danger  that  surface  waters  and  sewage 
may  seep  into  a  cistern  through  cracks  in  its  upper  walls. 
These  walls  should  always  be  so  laid  as  to  prevent  leakage 
into  the  cistern  as  well  as  leakage  out  from  it.  This  can  be 
accomplished  by  use  of  non-porous  brick  laid  in  cement  for 
the  walls,  and  by  having  the  inner  side  of  the  walls  plastered 
with  cement. 

The  aeration  of  the  waters  of  city  systems  is  accomplished 
in  various  ways.  In  cases  where  water  is  pumped  directly 
into  the  mains  enough  air  may  enter  with  the  water  to  keep 
it  thoroughly  aerated.  In  storage  reservoirs  arranged  on 
different  levels  above  one  another,  the  water  is  allowed  to 
flow  from  the  higher  to  the  lower  levels  in  long  thin  sheets, 
falling  with  more  or  less  of  spray  into  the  lower  reservoirs. 
Very  often,  too,  provision  is  made  for  filtering  these  waters 
through  layers  of  sand  and  gravel. 

In  dwellings  where  no  city  water  supply  is  available,  water 
from  cisterns  or  wells  is  sometimes  forced  into  large  steel 
cylinders  partly  filled  with  air.  By  reason  of  the  pressure 
of  the  compressed  air,  the  water  flows  through  pipes  to  all 
parts  of  the  house  so  long  as  the  air  pressure  is  maintained  by 
frequent  pumpings. 

SUMMARY 

The  provision  of  an  abundance  of  pure  water  for  household  and 
general  uses  is  indispensable  to  the  welfare  of  people  whether  living 
in  towns  or  in  rural  districts.  Sanitary  conditions  require  an  ample 
supply  of  water  for  the  removal  as  sewage  of  the  waste  matter  of  towns 
and  cities.  The  large  use  of  water  for  fire  protection,  for  street  clean- 
ing, for  homes,  for  public  laundries,  for  mills  and  factories  and  various 
other  industrial  plants,  makes  necessary  large  outlays  for  the  construc- 
tion and  maintenance  of  water  systems. 

The  utmost  vigilance  is  at  all  times  necessary  to  safeguard  the  water 


HEALTH  AND  WELL-BEING  57 

supply  on  the  farm  and  in  the  city.  Disease  germs  in  the  water  may 
cause  widespread  sickness  and  death.  Water  from  surface  wells  and 
streams  is  always  subject  to  suspicion  when  not  safeguarded  with  the 
greatest  care. 

The  source  of  the  water  supply  for  different  cities,  and  the  manner 
of  its  purification,  varies  according  to  local  conditions.  In  some  cases 
it  is  pumped  from  deep  wells  into  the  water  mains;  in  other  cases  it  is 
taken  from  rivers  or  lakes  and  stored  in  reservoirs  where  it  is  freed 
from  any  sediment  before  being  allowed  to  flow  into  the  distributing 
pipes.  Sometimes  certain  chemicals  are  introduced  to  hasten  the 
settling  of  suspended  matter,  and  in  other  cases  chemicals  are  used  to 
free  the  water  of  organic  matter  and  disease  germs  if  any  be  present. 
Some  definite  knowledge  of  the  water  system  of  one's  own  -city  is  a 
requisite  for  any  sufficient  understanding  of  conditions  affecting  the 
community  welfare. 

Apart  from  the  presence  of  disease  germs,  the  existence  in  drinking 
water  of  decaying  organic  matter,  whether  in  a  finely  divided  state  or 
in  solution,  is  a  source  of  sickness.  Oxidation  is  the  readiest  means 
of  freeing  water  of  organic  matter,  whether  of  animal  or  vegetable 
nature,  and  whether  from  sewage  or  from  decaying  vegetation. 

Cistern  water  may  be  kept  aerated  by  the  use  of  a  chain  pump. 
Running  water  in  streams  is  likely  to  have  become  purified  by  its 
exposure  to  the  air,  especially  where  its  volume  is  not  too  large  and 
where  its  current  is  more  or  less  broken.  The  stored  water  of  reser- 
voirs may  be  aerated  by  forcing  air  through  it  from  pipes  laid  in  the 
bottom  of  the  reservoir,  or  by  the  use  of  fountains  whose  spray  of 
water  falls  back  into  the  reservoir.  Where  water  is  pumped  into  the 
water  mains,  sufficient  air  for  its  aeration  may  be  made  to  enter  along 
with  the  water. 

GENERAL  HEALTH  PROBLEMS 

The  life  history  of  flies  and  mosquitoes  possesses  great 
interest  aside  from  the  possibility  of  their  becoming  carriers 
of  disease  germs.  A  study  of  the  structure  and  transforma- 
tions of  all  insect  life,  and  of  the  relations  of  insects  to  plants 
and  to  mankind,  is  a  field  of  science  of  unsurpassed  interest. 
Insects  are  of  utmost  economic  importance  to  man,  affecting 
his  health,  comfort,  and  prosperity  in  innumerable  ways. 


58  GENERAL  SCIENCE 

The  honeybee  and  the  silk  worm  contribute  to  his  well-being. 
But  in  spite  of  their  marvelous  beauty  of  form  and  coloring, 
and  all  the  wonder  which  their  structure  and  transformations 
and  adaptability  to  changing  conditions  may  call  forth, 
insects  are  generally  to  be  regarded  as  pests.  They  are  a 
destructive  agency  against  which  ceaseless  warfare  is  to  be 
waged.  There  are  more  known  species  (various  kinds)  of 
insects  than  there  are  species  of  all  other  animals  combined. 
So  great  is  the  number  of  insects  that  they  are  said  to  com- 
prise three-fourths  of  the  animal  kingdom.  Any  good  text 
on  animal  biology  will  furnish  information  of  greatest  worth 
concerning  insects.  We  do  not  need  to  be  scientists, 
however,  to  acquire  sufficient  knowledge  of  this  group  of 
animal  life  to  understand  how  our  health  and  comfort  are 
affected  by  them. 

In  a  general  way  the  bodies  of  insects  may  be  described  as 
consisting  of  head,  thorax,  and  abdomen.  On  the  head  are  a 
pair  of  relatively  large  eyes,  and  two  antennae  or  "feelers." 
Attached  to  the  thorax  are  two  pairs  of  wings  above,  and 
three  pairs  of  jointed  legs  below.  The  abdomen  is  made  up 
of  a  series  of  rings  or  segments.  Moths,  bees,  flies,  butter- 
flies, or  grasshoppers  may  be  chosen  for  making  studies  of 
insects.  A  pocket  lens  is  a  great  aid  in  making  these  studies. 

The  feet  and  body  of  the  common  house  fly  as  seen  under 
a  magnifying  glass  appear  hairy.  A  sticky  secretion  on  the 
feet  of  the  fly  enables  it  to  walk  on  smooth  surfaces,  and  in 
all  manner  of  positions.  As  the  common  house  fly  revels  in 
filth  of  all  kinds  it  is  a  menace  to  health  everywhere  it  goes. 
There  is  always  the  possibility  of  germs  of  typhoid,  tuber- 
culosis, or  dysentery  being  left  by  flies  on  foodstuffs,  and  on 
the  dishes  used  in  kitchen  and  dining  room.  The  female 
fly  may  lay  one  hundred  eggs  or  more  at  a  time,  and  under 
favorable  conditions  these  may  hatch  within  a  day.  The 
larva  (grubs,  or  maggots)  grow  rapidly,  especially  if  lodged 


HEALTH  AND  WELL-BEING 


59 


in  a  pile  of  horse  manure,  and  in  about  five  days  change  to 
the  pupa  stage.  In  another  week  the  full  grown  flies  emerge, 
and  the  cycle  of  changes  is  repeated.  Thus  it  is  that  in  about 
two  weeks  one  hundred  eggs  may  become  .one  hundred  flies. 
As  each  female  may  lay  four  lots  of  eggs  in  a  season  it  is 
possible  for  a  single  fly  to  be  multiplied  into  millions  between 
spring  and  fall. 


PIG.  24. — The  house  fly. 

Control  of  the  menace  from  flies  lies  in  the  fact  that  rela- 
tively few  flies  live  through  cold  winter  seasons,  and  that  they 
do  not  go  far  away  from  their  breeding  places.  The  survi- 
vors in  the  spring  may  be  trapped  and  the  conditions  for 
breeding  may  be  made  unfavorable  throughout  the  season. 
Piles^of  refuse  about  stables,  and  of  decaying  organic  matter 
anywhere,  are  favorite  breeding  places.  Any  successful 


6o 


GENERAL  SCIENCE 


warfare  upon  flies  requires  preventive  measures.  From  the 
earliest  springtime,  large  outdoor  flytraps  should  be  kept 
about  garbage  cans,  in  stables,  and  near  the  outer  doors  of 
kitchens  or  wherever  else  food  is  being  prepared  or  served. 

The  eggs  of  the  common  mosquito  are  found  floating  in 
stagnant  water.    Under  favorable  conditions  these  may  hatch 


W 


FIG.  25. — Life  history  of  the  mosquito.  i,  eggs;  2,  larva;  3,  pupa; 
4,  the  common  mosquito  (Culex).  WW,  water  level  below  which  larva 
and  pupa  almost  wholly  float.  This  makes  possible"  their  suffocation  with  a 
thin  layer  of  crude  petroleum  spread  over  the  water  surface. 

within  one  day.  The  larvae  (known  as  wrigglers)  after 
about  a  week  of  rapid  growth  enter  a  pupa  stage.  This 
state  continues  but  a  few  days  when  the  change  to  a  fully 
developed  mosquito  occurs.  In  waters  stocked  with  fish, 
these  wrigglers  are  devoured.in  large  numbers.  Where  water 
surfaces  of  stagnant  pools  in  marshes  are  covered  with  a 


HEALTH  AND  WELL-BEING  61 

thin  film  of  crude  petroleum,  the  mosquito  larvae  are 
smothered,  and  the  numbers  of  mosquitoes  in  any  locality 
during  a  season  is  materially  lessened. 

While  the  common  mosquito  culex  is  a  great  annoyance, 
the  malarial  mosquito  anopheles  (a-noi'-e-les)  is  a  direct 
menace  to  health.  (See  page  39.)  The  discovery  of  the 
germ  of  malaria  in  1880,  and  of  the  existence  of  malarial 
germs  within  the  body  of  the  mosquito  as  its  host,  with 
,  reasons  for  the  belief  that  without  the  mosquito  as  an  inter- 
mediary there  would  be  no  transmission  of  malaria  from  per- 
son to  person,  forms  a  wonderfully  interesting  story.  When 
a  malarial  germ  once  finds  entrance  into  the  blood  of  a  person, 
it  lives  and  subdivides  within  some  red  blood  corpuscle. 
After  a  period  of  a  few  days  the  corpuscle  is  broken  down, 
and  the  multiplied  germs  are  set  free  in  the  blood  to  enter 
other  red  corpuscles  where  further  multiplication  occurs. 
The  characteristic  chill  of  malaria  usually  follows  these 
periodic  liberations  of  the  malarial  germs  in  the  blood. 

One  of  the  problems  of  a  city  administration  is  the  removal 
of  garbage  economically  and  efficiently.  The  value  of  the 
waste  in  the  garbage  of  a  large  city,  including  various  metals, 
old  rubber,  cloth,  glass,  and  grease,  aggregates  great  sums 
annually.  Destruction  of  garbage  by  fire  removes  the 
menace  to  health  from  any  disease  germs  present  in  it.  The 
sewage  of  a  great  city  represents  an  enormous  loss  annually 
in  fertilizer  for  soils.  Sanitary  conditions,  however,  and  the 
cost  of  transportation  of  this  material  to  places  where  it 
could  be  used,  make  any  prevention  of  this  economic  waste 
largely  out  of  question. 

Rats  have  long  been  regarded  as  a  pest,  but  have  been 
tolerated.  The  waste  caused  every  year  by  their  depreda- 
tions on  farms,  in  warehouses,  in  dwellings,  on  shipboard 
and  elsewhere  is  enormous.  Since  their  agency  in  the  spread 
of  the  dread  bubonic  plague  has  been  established,  active 


62  GENERAL  SCIENCE 

measures  for  their  extermination  have  followed.  Rats  may 
become  infected  by  bites  of  fleas  that  have  bitten  plague- 
stricken  patients.  Wherever  these  rats  go  the  disease  germs 
may  in  turn  be  transmitted  from  the  rats  to  persons  by 
agency  of  fleas. 

In  these  days  of  cement  construction  there  is  no  excuse 
for  rat-haunted  dwellings  and  storehouses.  Hunting  and 
destroying  rats  on  an  extensive  scale  is  expensive.  Their 
extermination  can  be  accomplished  in  time  by  imposing 
appropriate  penalties  for  harboring  rats  upon  owners  of 
ships  and  buildings.  It  should  be  kept  in  mind  that  rats 
and  mice  remain  only  where  food  is  available  for  them,  and 
that  to  properly  protect  foodstuffs  at  house,  barn,  store, 
and  warehouse  from  depredations  of  rats  is  to  lessen  their 
numbers  if  not  entirely  to  be  rid  of  them. 

SUMMARY 

In  agriculture  the  destruction  wrought  by  insects,  especially  while 
in  the  larva  or  "worm"  stage,  is  almost  incalculable.  Insects  are  not 
only  a  pest  so  far  as  man's  comfort  goes,  but  they  are  a  menace  to  his 
health  and  to  life  itself. 

Insects  constitute  the  most  numerous  division  of  the  animal  kingdom. 
Between  the  egg  when  hatched,  and  the  fully  developed  insect  that 
in  turn  lays  eggs  for  another  generation,  there  are  variations  in  the 
length  of  time  required  by  different  species  to  complete  the  "cycle." 
There  are  differences  in  the  succession  of  changes  that  occur.  How- 
ever, from  the  eggs  come  the  larvae  variously  known  as  "worms,"  "mag- 
gots/* "grubs,"  or  "caterpillars;"  then  comes  the  pupa  or  "chrysalis" 
stage,  followed  by  that  of  the  grown  insect. 

Insects  in  general  are  characterized  by  having  the  three  parts  head, 
thorax,  and  abdomen.  The  eyes  and  antennae  are  parts  of  the  head; 
to  the  thorax  are  attached  the  legs  and  wings;  and  the  abdomen  is 
made  up  of  connected  ring-like  parts. 

While  there  are  many  kinds  of  flies,  some  of  which  are  tormenters 
of  both  men  and  animals,  the  common  house  fly  as  a  carrier  of  filth  and 
disease  germs  should  be  exterminated  as  a  sanitary  measure. 

The  discovery  of  the  part  played  by  some  kinds  of  mosquitoes  in  the 


HEALTH  AND  WELL-BEING  63 

spread  of  certain  diseases,  and  the  logical  application  of  this  knowledge 
to  other  health  conditions,  constitutes  one  of  the  brightest  pages  in 
the  history  of  preventive  medicine. 

In  the  increased  use  of  cement  for  building  purposes  lies  one  of  the 
chief  aids  in  the  warfare  upon  rats  and  mice.  Without  access  to  food 
supplies,  starvation  will  keep  their  numbers  down.  They  are  a  menace 
to  health  as  carriers  of  disease,  and  their  destruction  of  foodstuffs  and 
other  property  necessitates  their  extermination.  Freedom  from  vermin 
of  all  kinds  is  an  indispensable  sanitary  measure. 


FIG.  26. — A  breeding  place  for  house  flies. 


Exercises 

1.  Name  various  ways  in  which  the  waters  of  wells  near  dwellings  and 
farm  buildings  are  likely  to  become  contaminated. 

2.  How  may  surface  drainage  into  wells  be  prevented? 

3.  Describe  the  action  of  "chain  pumps"  as  means  for  the  aeration  of 
cistern  waters. 

4.  Why  are  cisterns  as  sources  of  water  for  household  uses  in  large  towns 
and  cities  quite  out  of  question? 

5.  How  may  the  stored  waters  of  large  reservoirs  in  city  water  systems  be 
aerated? 


64  GENERAL  SCIENCE 

6.  How  may  the  presence  of  disease  germs  in  any  sample  of  water  be 
determined? 

7.  Why   are   such    vigorous   campaigns    waged    to   exterminate    flies    and 
mosquitoes? 

8.  Why  is  it  that  the  "scale"  forming  on  the  inside  of  boilers  is  so  seriously 
objectionable? 

9.  Of  what  service  is  water  in  the  nutrition  of  the  body?     Discuss  how  it  is 

that  the  abundant  use  of  water  internally  contributes  to  health  and 
length  of  life. 

10.  In  a  general  way  what  duties  and  responsibilities  rest  upon  every    in- 
dividual in  any  community  as  to  matters  of  public  health? 

11.  In  what  perfectly  honest  way  may  it  be  possible  for  a  dealer  in  food- 
stuffs to  be  able  to  sell  at  lower  prices  than  some  of  his  competitors? 
Name  some  dishonest  forms  of  competition  in  the  preparation  and  sale 
of  foodstuffs. 

LIFE,  GROWTH,  REST,  AND  RECREATION 

Under  the  microscope  it  is  found  that  both  plant  and 
animal  tissues  are  made  up  of  cells.  While  there  is  a  wide 
variation  among  cells  in  form  and  arrangement,  and  in  other 
respects,  every  living  cell  consists  essentially  of  a  more  or 
less  fluid  content  known  as  protoplasm.  This  possesses  life, 
and  it  has  the  powers  of  growth  and  of  subdivision.  Food 
for  plants  and  animals  includes  all  the  material  required  to 
build  new  cell  walls,  to  nourish  the  protoplasm,  and  to 
furnish  the  energy  required  in  keeping  the  organs  of  the  body 
active. 

The  outer  portions  of  the  hair,  skin,  and  nails,  as  well  as 
those  growths  known  as  corns,  warts,  and  callouses,  consist 
largely  of  layers  of  dead  cells.  These  are  pushed  outward 
and  away  from  the  living  growing  tissues  underneath.  A 
lessened  blood  supply  to  any  such  part  of  the  body  where 
unnatural  cell  growth  is  taking  place  may  hinder  and  in  time 
stop  the  undesirable  growth. 

In  trees  the  greater  part  of  the  wood  structure  consists  of 
cells  largely  or  wholly  destitute  of  life.  So  long  as  these  are 
enveloped  by  living  tissue,  however,  decay  of  the  wood  does 


HEALTH  AND  WELL-BEING  65 

not  occur.  There  is  an  increase  in  the  size  of  the  tree  by 
reason  of  the  added  annual  wood  formation.  In  animal  life, 
on  the  other  hand,  prompt  removal  from  the  body  of  the 
dead  cells  of  the  tissue  by  oxidation  or  otherwise  is  necessary 
for  the  maintenance  of  health. 

Irritation  of  any  organ,  or  of  any  part  of  the  body,  causing 
an  excessive  blood  supply  there  and  a  congestion  of  its  blood 
vessels,  stimulates  excessive  secretions  and  a  cell-building 
that  is  likely  to  be  unnatural  in  character.  The  high  tem- 
perature of  the  inflamed  region  is  likely  to  affect  unfavorably 
the  protoplasm  of  the  cells.  With  the  system  unable  to  rid 
itself  rapidly  enough  of  waste  matter,  illness  follows.  Medi- 
cines may  be  required  both  to  remove  the  cause  and  to  stimu- 
late the  organs  of  the  body  to  a  more  prompt  removal  of  the 
waste  material. 

Sustained  mental  activity  of  a  high  order  requires  a  well- 
balanced  physical  development.  All  organs  of  the  body, 
including  the  brain  and  nervous  system,  must  be  in  a  healthy 
and  well-nourished  state.  Apparent  exceptions  to  this  rule 
may  be  explained  (though  not  accounted  for)  by  saying  that 
mental  activity  occurs  in  spite  of  bodily  infirmities,  and  that 
it  is  always  limited  more  or  less  by  them.  It  may  be  con- 
sidered true  generally  that  health  and  efficiency  are  through- 
out life  directly  dependent  upon  wisely  ordered  bodily  ac- 
tivities. The  brain  and  nervous  system  can  be  kept  in  tone 
and  vigor  only  through  sufficient  and  suitable  exercise  of  the 
whole  muscular  system.  On  the  other  hand,  the  mind  is 
largely  independent  of  abnormal  muscular  development  and 
of  excessive  bodily  strength.  A  "  sound  mind  in  a  sound 
body"  has  no  necessary  reference  to  physical  prowess  and 
athletic  training. 

Any  cells  of  the  body  if  kept  inactive  become  less  vigorous, 
and  finally  die  as  a  result  of  disuse.  The  muscles  unused 
become  weak  and  flabby.  Activity  in  all  tissues  is  essential 


66 


GENERAL  SCIENCE 


to  their  healthful  state,  and  this  is  as  true  of  the  brain  and 
nervous  system  as  of  other  parts  of  the  body.  The  person 
who  maintains  many  interests  in  life,  and  a  variety  of 
activities  both  mental  and  manual,  is  not  only  likely  to 
lengthen  life  thereby  but  to  add  to  it  many  years  of  efficiency 
and  of  enjoyment  in  living. 

Rest  is  essential  for  both  body  and  mind  that  their  activi- 
ties may  be  continued.  The  human  body  as  a  machine  at 
work  does  not  provide  energy  rapidly  enough,  nor  make 


FIG.  27. — Gardening  is  good  exercise. 

tissues  fast  enough,  to  keep  up  with  the  waste.  Unlike 
ordinary  machines  it  is  rebuilding  its  parts  as  it  goes  along. 
This  requires  time,  and  favorable  conditions,  and  a  suitable 
food  supply.  Sleep  is  needful  to  keep  the  body  vigorous 
and  in  a  healthy  state.  Those  hours  that  are  spent  in  sound 
refreshing  sleep  are  not  wasted.  Sleep  to  be  refreshing 
should  be  free  from  disturbances  and  interruptions,  and  from 
the  ill-effects  of  an  intemperate  diet. 

Eight  hours  per  day  is  enough  sleep  for  people  generally. 


HEALTH  AND  WELL-BEING 


67 


But  excessive  labor  of  any  kind,  and  the  wear  incident  to  it, 
may  require  a  correspondingly  longer  period  to  rebuild 
tissues  and  restore  the  energy  of  the  body.  Children  during 
the  years  of  their  growth  require  more  sleep  than  adults. 


FIG.  28. — School  gardens. 


Sitting  up  late  at  night  for  study  as  practised  by  students  in 
school  is  not  generally  advisable.  Social  indulgencies  that 
carry  festivities  late  into  the  night  are  to  be  wholly  avoided. 
Physical  weariness  when  not  excessive  is  conducive  to  sleep, 


68  .  GENERAL  SCIENCE 

and  oftentimes  sleeplessness  is  a  direct  result  of  insufficient 
physical  exercise. 

The  human  body  cannot  manufacture  something  out  of 
nothing.  A  healthy  cell  growth,  and  a  vigorous  protoplasm, 
is  a  natural  result  of  a  temperate  and  simple  manner  of  life. 
Intemperance  in  matters  of  food,  sleep,  drink,  occupations, 
and  amusements  dissipates  the  energies,  and  proves  destruc- 
tive to  health  and  to  life  itself. 

When  machinery  of  the  ordinary  kind  wears  out  or  breaks 
down,  it  can  be  thrown  on  the  scrap  heap,  and  new  machines 
put  in  its  place.  But  it  is  difficult  to  conceive  that  any  sane 
person  will  deliberately  choose  a  course  in  life  that  must 
inevitably  lead  to  his  breakdown  in  body  and  mind.  Ignor- 
ance of  violations  of  the  laws  of  well-being,  and  of  the  results 
of  any  departure  from  the  ways  of  right  living,  does  not 
change  those  results.  Enlightenment  as  to  the  conditions 
for  attaining  and  maintaining  physical  and  mental  vigor  con- 
stitutes one  of  the  most  important  parts  of  school  instruction. 

Recreation  seeks  that  restoration  of  body  and  mind  which 
makes  possible  the  best  efforts  of  both.  There  is  little  need 
to  remain  long  in  doubt  whether  any  particular  course  in 
life  is  recreation,  or  is  instead  a  dissipation  of  one's  energy 
and  powers.  While  in  amusements  there  is  oftentimes  no 
thought  other  than  of  pleasure,  rest  and  invigoration  should 
always  result  from  them.  Here  as  elsewhere,  the  dividing 
line  between  recreation  and  dissipation  may  be  quickly 
discerned  by  one  who  is  thoughtful  of  his  own  well-being  and 
of  the  welfare  of  others.  It  is  a  law  of  human  life  that  any 
right  use  of  time  and  strength,  and  of  the  powers  of  body 
and  of  mind,  brings  increase  in  ability  to  do ;  their  disuse  or 
misuse  renders  one  less  capable.  It  is  indispensable  to  health 
and  happiness  that  one  avoid  all  those  pleasures  that  overtax 
the  bodily  energy  or  tend  toward  disease  and  immorality  of 
any  kind. 


HEALTH  AND  WELL-BEING  69 

The  games  and  sports  of  childhood  and  youth  furnish 
much  of  the  exercise  essential  to  the  development  of  healthy 
and  vigorous  bodies.  They  make  possible  more  enjoyment 
in  living,  and  greater  ability  to  do  well  the  labors  that  devolve 
upon  one  throughout  life.  In  rural  communities  a  wide 
range  of  wholesome  occupations  and  out-of-door  sports  is 
always  possible;  in  towns  and  cities  these  opportunities  are 
more  or  less  restricted.  So  important  is  play  considered  by 
those  who  have  at  heart  the  interests  of  children  and  of 
society  at  large  that  special  effort  is  made  in  cities  to  provide 
properly  supervised  sports  and  physical  training  for  both 
boys  and  girls. 

Aside  from  any  outlays  involved,  the  nature  of  one's  em- 
ployment in  life  should  dictate  very  largely  the  forms  of 
recreation  chosen.  In  a  general  way  the  best  results  are 
attained  from  those  amusements,  recreations,  and  enter- 
tainments in  which  there  is  the  most  of  enjoyment  and  of 
restfulness.  The  benefits  from  being  an  on-looker  at  games 
and  plays  is  very  generally  far  short  of  what  might  result 
from  actual  participation  in  them.  This  is  especially  the 
case  in  active  out-of-doors  sports  and  occupations.  No 
one  could  reasonably  think  of  being  nourished  by  food  eaten 
by  another,  or  of  growing  intellectually  as  result  of  getting 
some  one  else  to  do  his  thinking  for  him.  It  is  a  great  pity 
for  people  to  deceive  themselves  into  being  content  with  not 
taking  part  in  sports  and  other  forms  of  physical  exercises. 

Any  excessive  amount  of  time  or  attention  given  over  to 
amusements  or  to  sleep  constitutes  intemperance  in  living, 
even  as  does  excessive  labor  of  muscles  or  brain,  or  over- 
indulgence in  eating  and  drinking. 

It  is  the  experience  of  the  human  race  that  besides  the 
natural  rest  periods  given  over  to  sleep,  the  welfare  of 
individuals  throughout  life  requires  an  additional  one  day 
out  of  every  seven,  approximately  if  not  literally,  in  which 


70  GENERAL  SCIENCE 

the  usual  routine  of  life  is  set  aside1.  This  time  should  be 
so  used  as  to  rest  the  worker,  and  to  elevate  his  intellectual 
and  moral  life. 

Sports  and  games  are  forms  of  amusement  in  which  there 
should  be  a  combination  of  suitable  physical  exercise  and  a 
rational  mental  activity,  with  sometimes  one  and  sometimes 
the  other  dominating.  The  greatest  enjoyment  and  largest 


FIG.   29. — A  restful  scene. 

benefit  comes  from  out-of-doors  sports,  and  from  games 
played  for  the  fun  there  is  in  them  rather  than  for  commer- 
cialized or  competitive  ends. 

To  permit  one's  self  to  become  intensely  wrought  up,  and 
to  experience  any  long  sustained  excitement  in  witnessing 
professional  games  or  plays  presented  upon  the  stage,  may 
be  exhausting  in  its  results  rather  than  restful  and  recupera- 

1  In  this  connection  it  is  to  be  observed  that  the  "Ten  Commandments" 
delivered  to  the  Israelites  by  Moses  for  their  welfare  as  individuals,  and 
for  their  existence  as  a  nation,  laid  stress  upon  the  requirement  "Six  days 
shall  thou  labor"  as  well  as  upon  setting  apart  the  seventh  day  as  a  day  of 
rest  and  religious  observances. 


HEALTH  AND  WELL-BEING  71 

tive.  In  all  cases  where  participation  in  games  and  sports 
is  impossible,  and  where  they  are  promoted  as  money- 
making  schemes,  it  is  always  well  to  consider  carefully 
whether  indulgence  in  them  is  not  likely  to  become  dissipa- 
tion rather  than  recreation. 

It  does  not  require  any  large  amount  of  observation  of 
effects  to  determine  whether  or  not  any  particular  form  of 
amusement  benefits  or  harms  one  physically,  and  whether  it 
interferes  with  the  discharge  of  one's  duties;  whether  it 
refines  and  uplifts  one's  ideals  of  life,  or  tends  to  brutalize 
and  degrade  them.  Nor  does  it  require  any  large  amount  of 
ability  to  plan  and  accomplish  much  in  the  way  of  providing 
pleasurable  and  restful  occupations  about  the  home,  and  in 
connection  with  home  life. 

SUMMARY 

The  human  body  is  a  structure  built  up  of  units  known  as  cells. 
The  same  is  true  of  other  animals,  and  of  plants.  These  cells  are  of 
many  forms,  and  they  have  widely  different  uses.  All  living  cells 
essentially  consist  of  a  semi-fluid  content  known  as  protoplasm.  It  is 
the  "living  matter"  of  the  body.  Growth  in  the  body  is  the  result  of 
a  subdivision  of  the  cells  due  to  activities  of  the  protoplasm.1 

The  cells  get  nourishment  from  the  watery  fluid  by  which  they  are 
surrounded.  This  lymph  is  much  like  the  watery  part  of  the  blood. 
Into  it  the  cells  discharge  their  waste,  and  this  sooner  or  later  gets 
into  the  blood.  Once  inside  the  blood  vessels,  it  is  carried  in  the  round 

1  Attention  is  called  here  to  a  theory  of  biological  science  which  is  funda- 
mental in  its  importance,  viz.,  that  the  "life"  in  every  living  form  has  been 
transmitted  from  some  earlier  existing  parent  life.  Each  successive  genera- 
tion of  plants  and  of  animals  has  life  because  of  cell  protoplasm  derived  from 
a  parent  plant  or  animal.  In  other  words,  there  is  no  such  thing  as  "spon- 
taneous generation"  of  life,  and  no  creation  of  life  energy  any  more  than  with 
other  forms  of  energy.  This  implies  that  in  a  remote  past  there  must  have 
been  a  time  when  "In  the  beginning"  there  was  a  creation  of  life  making 
possible  the  continuity  with  which  the  study  of  biological  science  makes  us 
acquainted.  Concerning  any  such  time  and  creative  act  science,  of  course, 
teaches  nothing. 


72  GENERAL  SCIENCE 

of  circulation  to  the  special  organs  by  which  it  is  eliminated  from  the 
body. 

The  great  value  to  health  of  suitable  exercise  lies  in  an  increased 
activity  of  the  cells,  a  larger  supply  of  nourishment  brought  to  them, 
and  a  more  complete  riddance  of  the  waste  of  the  body  from  the  cells 
and  tissues. 

The  brain  as  organ  of  the  mind  requires  nourishment,  exercise,  and 
freedom  from  exhaustive  labors  for  its  growth  and  activities  even  as 
other  parts  of  the  body. 

The  need  of  rest  for  the  human  body,  including  those  periods  of 
sleep  when  complete  relaxation  should  occur,  results  from  the  fact  that 
the  human  body  does  not  rebuild  its  cells  rapidly  enough,  nor  provide 
energy  sufficiently  fast,  to  make  good  the  waste  of  the  body  in  its 
hours  of  activity. 

Recreations  may  be  considered  as  including  all  those  occupations 
where  the  general  results  are  restful.  Recreation  ranges  in  character 
from  what  is  done  solely  as  amusement  to  what  is  merely  a  change  in 
form  of  labor.  This  latter  is  restful  because  it  calls  into  use  activities 
of  the  body  before  unused,  thus  freeing  those  parts  which  have  become 
wearied. 

STIMULANTS  AND  NARCOTICS 

There  is  a  certain  rate  at  which  an  engine  or  dynamo  does 
its  best  work,  and  where  there  is  the  least  wear.  Both  its 
efficiency  as  a  machine  and  its  length  of  life  as  a  working 
agent  require  that  it  be  run  at  its  normal  capacity.  To 
overload  a  dynamo  or  a  steam  engine,  or  to  speed  either 
beyond  a  normal  rate,  means  its  destruction.  The  human 
body  in  spite  of  its  recuperative  powers  suffers  from  the  wear 
and  waste  of  an  unnatural  strain  put  upon  it  in  the  use  of 
alcoholic  drinks,  and  sooner  or  later  breaks  down.  The  vital 
organs  are  affected  seriously,  and  it  is  upon  them  that  length 
of  life  and  vigor  of  health  largely  depends.  One  may  live 
long  and  be  an  active  agent  in  the  affairs  of  life  after  the 
system  is  incapacitated  for  hard  muscular  labor;  but  there 
is  always  a  need  for  vigorous  heart  action,  active  nutritive 
processes,  and  healthy  action  of  kidneys  and  lungs.  The 


HEALTH  AND  WELL-BEING  73 

remedy  at  any  time  for  lack  of  vigor  and  strength,  whether 
of  body  or  mind,  is  not  some  stimulant  to  further  use  up  the 
scant  store  of  energy,  but  hygienic  living  in  order  that  the 
physical  conditions  be  such  as  to  provide  the  needed  strength. 

Only  workmen  with  clear  minds,  skillful  hands,  and  steady 
nerves  are  wanted  in  the  railway  service,  in  the  great  indus- 
tries, and  in  all  positions  of  trust  and  responsibility.  Dissipa- 
tion of  any  sort  shatters  the  nerves,  beclouds  the  brain,  and 
unfits  for  effective  service.  Such  workers  are  discriminated 
against  in  the  affairs  of  the  world  everywhere  and  cannot 
hope  to  secure  and  retain  its  most  desirable  positions. 

The  continued  use  of  small  amounts  of  alcoholic  liquors 
impairs  the  health,  reduces  the  recuperative  powers  of  the 
body  in  cases  of  illness,  and  makes  one  more  liable  to  in- 
fectious diseases.  Insurance  companies  often  refuse  to 
take  life  risks  of  even  moderate  drinkers  because  of  the 
higher  death  rate  among  them. 

The  debauching  effects  of  an  excessive  use  of  alcoholic 
drinks  is  a  matter  of  common  observation;  and  the  use  of 
alcohol  as  a  beverage  is  a  menace  to  human  life  and  social 
welfare.  The  testimony  of  texts  on  human  biology  con- 
cerning its  destructive  results  upon  the  nerve  centers  that 
are  concerned  in  the  higher  intellectual  processes  is  scarcely 
required.  The  drinker  is  not  only  made  less  efficient 
physically  and  mentally,  but  he  loses  in  self-respect,  and 
his  powers  of  judgment  are  impaired. 

Poverty,  wretchedness,  vice,  and  crime  are  common 
accompaniments  of  the  habitual  and  excessive  use  of  alco- 
holic drinks  and  narcotics.  At  no  time  does  the  victim  of 
alc'oholic  drink  plan  to  make  a  wreck  of  his  life  and  man- 
hood by  becoming  hopelessly  enslaved.  His  helplessness 
in  an  attempt  to  regain  wasted  strength  of  body,  and  to 
reassert  control  over  himself,  calls  for  pity.  In  his  home 
there  are  those  who  are  innocent  sufferers,  and  the  com- 


74  GENERAL  SCIENCE 

munity,  too,  suffers  loss  in  the  worth  and  excellence  of  its 
citizenship. 

Parents  who  are  users  of  alcoholic  drinks  are  responsible 
for  lessened  vitality  in  their  children  due  to  alcohol.  The 
children  of  such  parents  are  often  afflicted  by  physical 
weaknesses,  and  are  less  likely  to  live  through  infancy. 

So  readily  does  one  become  a  victim  of  an  uncontrollable 
appetite  for  habit-forming  drugs  and  alcoholic  drinks  that 
self-protection  makes  it  necessary  to  shun  the  company  of 
those  who  indulge  themselves  regardless  of  the  risks  taken. 


w~ 

nfmm 

±    JL    JL    1      1 

.     .• 

D   MALE 
O    FEMALE 

fmf. 

A  -  ALCOHOLIC 
•  •  FEEDLEMIMDED 

FIG.  30. — Laws  of  heredity  are  well  established  for  both  plants  and  ani- 
mals. The  diagram  shows  what  is  likely  to  be  true  of  children  and  grand- 
children where  a  man  addicted  to  the  use  of  alcoholic  drinks  marries  a  feeble- 
minded woman.  The  histories  of  such  unions  confirm  experimental  results 
in  the  breeding  of  plants  and  of  the  lower  animals. 

It  is  only  an  exercise  of  good  judgment  to  avoid  any  com- 
panionship and  all  social  relationships  where  the  price  is 
likely  to  be  the  undermining  of  the  health,  and  slavery  to 
the  use  of  intoxicating  liquors  and  narcotics. 

Boys  beginning  the  use  of  tobacco  should  have  knowledge 
of  the  fact  that  the  use  of  it  very  often  seems  to  prevent  a 
proper  development  of  body  and  mind.  Only  a  small  per 
cent  of  school  boys  who  are  confirmed  smokers  are  able 
to  keep  their  standing  in  school  work,  or  later  to  secure  and 
retain  the  most  desirable  positions,  Alcohol  and  narcotic 


HEALTH  AND  WELL-BEING  75 

Jrugs  are  never  to  be  used  in  any  form  save  as  prescribed 
by  a  physician,  and  are  always  to  be  shunned  the  same  as 
other  poisons. 

Perhaps  one  of  the  most  notable  outgrowths  of  the  great 
world  war  of  this  generation  has  been  the  restrictions  imposed 
by  the  warring  nations  upon  traffic  in  intoxicating  drinks. 
In  Russia  this  at  one  time  amounted  to  a  prohibition  of  the 
manufacture  and  sale  of  vodka,  the  national  drink.  The 
government  of  China  years  ago  awoke  to  the  debauching 
effect  upon  its  people  of  the  extended  use  of  opium.  But  it 
has  been  within  the  last  few  years  only  that  conditions  have 
become  favorable  for  the  stamping  out  of  its  unspeakable 
evils. 

Through  national  legislation  known  as  the  Harrison  law 
(1914),  the  American  people  have  at  last  resorted  to  drastic 
measures  to  restrict  the  increase  in  a  traffic  in  narcotics  that 
had  come  to  number  its  victims  in  all  parts  of  this  country 
by  the  thousands.  It  not  only  impoverishes  them  as  indi- 
viduals, but  it  wrecks  them  in  body  and  mind,  and  their 
degeneracy  constitutes  a  standing  menace  to  the  peace  of 
society.  This  law  seeks  so  to  control  the  dispensing  of  the 
more  powerful  narcotics  and  habit-forming  drugs  (except 
alcohol)  that  their  use  shall  be  solely  for  medical  pur- 
poses and  not  at  all  for  dissipation.  Society  has  not  hesi- 
tated here  to  deny  to  the  individual  the  right  to  ruin  himself, 
becoming  a  burden  to  his  family  and  to  the  community 
rather  than  a  constructive  factor  in  both.  It  has  under- 
taken to  punish  those  who  seek  profit  in  this  traffic  regard- 
less of  individual  and  public  welfare. 

The  activities  of  very  many  of  the  organs  of  the  body  are 
maintained  by  impulses  from  nerve  centres  not  controlled 
by  the  will,  and  these  activities  are  sustained  independently 
of  any  attention  or  thought  on  the  part  of  a  person.  A  great 
many  of  a  person's  voluntary  acts  and  efforts,  too,  may  be.- 


76  GENERAL  SCIENCE 

come  more  or  less  automatic  after  a  time.  The  control  of 
them  as  exercised  by  a  person  in  early  life  may  be  almost  or 
wholly  lost. 

Where  any  certain  sensation  is  received  over  and  over  again 
at  any  nerve  centre,  and  the  reaction  to  it  results  in  nerve 
impulses  that  bring  about  the  same  kind  of  an  act,  there 
comes  a  time  when  the  mind  gives  these  sensations  no  further 
special  attention.  The  reaction  (motor  impulse)  occurs 
when  the  sensation  is  received  without  any  considerable 
thought  being  given  to  it.  A  "nerve-track"  of  sensory  and 
motor  impulses  has  been  established  through  the  nerve  centre 
that  may  not  at  all  involve  conscious  effort  of  will.  Only  by 
exercise  of  long-sustained  and  powerful  self-restraint  can 
these  motor  impulses  be  brought  again  under  control  of  the 
will,  and  the  physical  condition  within  the  nervous  system 
changed.  Physiologists  thus  explain  "habit"  as  a  state  of 
the  body. 

Long  continued  use  of  alcohol  even  in  small  portions  so 
affects  the  nerve  centres  as  to  destroy  more  or  less  com- 
pletely the  power  to  control  acts  prompted  by  certain 
sensations  known  as  "cravings,"  or  an  abnormal  appetite. 
Even  the  sight  or  smell  of  liquor  may  arouse  desires  that  are 
not  controllable  by  the  victim  of  alcoholism.  These  cravings 
constitute  the  misery  and  unspeakable  torture  endured  by 
those  who  have  become  slaves  of  "habit-forming"  drugs  and 
preparations  when  they  are  denied  the  ever-increasing 
amounts  demanded  by  the  shattered  nervous  system,  or 
when  they  are  struggling  to  be  free  of  these  habits.  The 
knowledge  that  the  craving  is  relieved  by  a  further  supply 
of  the  drug  becomes  sufficient  incentive  for  any  act  that  will 
furnish  relief  for  the  craving. 

The  users  of  patent  medicines  are  always  in  danger  from 
these  evils.  Most  of  such  medicines  depend  upon  narcotics 
in  them  to  afford  relief  from  pain  or  to  bring  about  sleep, 


HEALTH  AND  WELL-BEING  77 

and  upon  their  alcoholic  content  to  arouse  an  entirely  false 
hope  of  speedy  recovery  from  illness.  Only  a  trained  and 
experienced  physician  may  safely  be  trusted  to  determine 
the  nature  of  any  serious  ailment  (" diagnose"  it),  and  to 
prescribe  the.  treatment  to  remove  its  cause. 

"Soothing  syrups"  for  infants,  and  " headache  powders" 
for  adults,  depend  upon  the  presence  of  powerful  narcotics 
in  small  quantities  to  deaden  pain,  and  to  induce  a  more  or 


FIG.  31. — Percentage  of  alcohol  in  a  patent,  medicine  formerly  having 
a  large  sale. 

less  unnatural  sleep.  Continued  use  of  soothing  syrups  and 
"colic  cures"  with  infants  is  likely  to  stunt  their  development 
in  body  and  mind,  and  leave  them  sickly  and  unfitted  to 
ward  off  the  diseases  of  infancy  and  childhood.  The  various 
cough  mixtures,  remedies  for  catarrh,  and  "cures"  for  colds 
are  likely  to  contain  narcotics  whose  purpose  is  to  deaden  the 
sensibility  of  the  inflamed  linings  of  throat  and  air  passages. 
While  temporary  relief  in  some  cases  may  be  experienced, 
the  system  at  large  is  seriously  deranged  by  use  of  these 
drugs.  That  the  ill-effects  of  these  drugs  may  not  be  imme- 
diately apparent  does  not  lessen  the  harm  wrought  every 
time  they  are  administered,  nor  avert  the  risks  taken  in 


78  GENERAL  SCIENCE 

their  use.  Even  the  reputable  physician  who  has  a  full 
understanding  of  the  physical  condition  of  the  patient  should 
be  exceedingly  cautious  in  prescribing  any  habit-forming 
drugs1.  The  use  of  medicines  at  all  times  is  chiefly  for  the 
purpose  of  bringing  about  conditions  of  the  body  favorable 
for  its  recuperative  powers.  Drugs  afford  at  the  best  but  a 
negligible  amount  of  energy  or  nourishment  for  the  body, 
and  contribute  nothing  to  the  store  of  "life"  as  it  exists  in 
the  protoplasm  of  the  cells. 

No  discussion  of  the  abuse  of  various  drugs  and  prepara- 
tions to  benumb  the  nerve  centres,  and  produce  an  unnatural, 
unconscious  state,  is  complete  without  mention  of  the  bless- 
ings to  humanity  in  the  use  of  anesthetics.  The  use  of  the 
vapors  of  ether  and  of  chloroform  to  produce  insensibility 
to  pain  in  the  extraction  of  teeth  by  dentists,  and  as  used 
extensively  by  physicians  and  surgeons  in  their  practice, 
dates  back  to  the  years  1844-1847.  The  freedom  from 
torture  under  the  knife  of  the  surgeon,  and  the  relief  given  in 
times  of  excruciating  pain  by  administering  an  anaesthetic, 
can  be  fully  appreciated  only  by  those  who  have  had  some 
experience.  The  elimination  of  the  exhaustion  from  endur- 
ance of  suffering,  and  the  avoidance  of  the  shock  to  the 
nerve  centres  resulting  from  great  pain,  make  likely  a 
more  prompt  rally  and  a  more  speedy  recovery  than  other- 
wise would  occur.  It  must  not  be  overlooked  that  adminis- 
tering an  anaesthetic  is  always  attended  by  risk  to  life,  and 
that  preferably  it  should  be  given  by  an  experienced  physi- 
cian only. 


1  In  the  gth  Revision  of  the  U.S.  Pharmacopoeia  (Sept.,  1916),  an  authority 
on  medicinal  preparations  used  in  this  country  and  recognized  as  a  standard 
in  all  courts  of  law,  no  use  of  whisky,  brandy,  or  wines  as  medicines  is 
included.  Alcohol  has  an  industrial  use  as  a  solvent  of  various  substances 
which  have  medicinal  value,  but  such  preparations  are  used  in  spite  of  their 
alcoholic  content  rather  than  because  of  it. 


HEALTH  AND  WELL-BEING  79 

SUMMARY 

Alcohol  and  the  narcotic  drugs  act  powerfully  upon  the  nerve  centres 
of  the  body.  The  effect  is  to  deaden  them  temporarily.  As  a  result 
the  activities  of  the  various  organs  of  the  body  are  deranged,  and  the 
energies  of  the  body  are  used  in  overcoming  the  ill-effects  experienced. 
The  irritated  nerves  in  the  various  tissues  affected  by  the  alcohol  rouse 
the  whole  system  to  increased  activities,  and  this  is  followed  by  a 
period  of  depression  both  physical  and  mental. 

Any  continued  use  either  of  alcohol  or  of  any  narcotic  is  likely  to 
produce  such  an  irritated  state  of  the  nervous  system  as  to  demand 
further  deadening  effects  upon  it  to  satisfy  the  "craving"  that  has 
been  aroused.  The  victim  of  the  "drug  habit"  or  of  alcoholic  drink 
finds  relief  only  in  further  indulgences. 

The  protoplasm  of  the  cells  is  harmfully  affected,  interfering  with 
the  growth  and  nourishment  of  the  brain  and  of  the  whole  body.  So 
serious  is  this  that  the  chances  of  recovery  from  sickness  of  any  kind 
is  found  to  have  been  lessened  by  even  moderate  use  of  alcoholic  drinks. 

The  use  of  tobacco  during  youth  interferes  with  growth  as  cell  division, 
stunting  more  or  less  the  development  of  the  brain  and  of  the  rest  of 
the  body. 

Powerful  drugs  of  any  kind,  including  alcohol  and  the  various  nar- 
cotics, should  never  be  used  save  upon  the  written  prescription  of 
a  skilled  physician,  and  only  after  a  personal  examination  by  him  to 
determine  the  exact  nature  of  any  ailment.  It  is  but  a  remote  chance 
that  the  drugs  contained  in  a  patent  medicine  will  prove  the  best 
treatment  for  any  one  whose  health  is  impaired. 

By  reason  of  the  stimulating  effect  of  the  alcohol  contained  in  a 
patent  medicine,  and  the  deadening  effect  of  its  narcotics  on  any  pain 
experienced,  false  hopes  of  recovery  are  aroused  by  its  use  only  to  be 
cruelly  disappointed.  The  time  thus  lost  may  make  impossible  any 
recovery  later  even  under  skilled  medical  treatment. 

Soothing  syrups  and  colic  cures  for  infants,  and  headache  powders 
for  adults,  contain  narcotics  in  varying  proportions,  and  should  never 
be  used  save  under  medical  advice. 

The  introduction  of  anaesthetics  for  use  in  dentistry,  in  surgery,  and 
in  medical  practice  generally,  has  conferred  an  almost  priceless  benefit 
upon  suffering  humanity. 

Under  the  provisions  of  national  legislation  in  the  so-called  Harrison 
Act  regulating  the  sale  of  narcotics,  it  is  sought  to  have  a  written 
record  of  sales  from  the  importer  or  manufacturer  to  the  consumer. 


8o  GENERAL  SCIENCE 

Druggists,  physicians,  and  any  others  licensed  to  dispense  these  drugs, 
are  held  responsible  under  heavy  penalties  for  any  use  of  them  for 
other  than  medical  purposes.  No  sales  are  permitted  for  purposes  of 
dissipation  on  the  part  of  those  who  have  the  drug  habit. 

Where  like  sensations  are  always  followed  by  the  same  kind  of 
responses,  the  brain  in  time  gives  less  and  less  attention  to  either  the 
sensations  or  the  responses.  There  comes  about  a  condition  where 
nerve  centres  other  than  those  involved  in  making  choices  and  direct- 
ing the  acts  of  an  individual  take  care  of  the  whole  matter.  Indeed, 
so  far  may  this  loss  of  the  will  power  over  these  acts  have  gone  that 
reason  and  will  seem  to  be  unable  to  regain  control  over  them.  The 
person  so  far  as  that  particular  habit  is  concerned  is  a  hopeless  slave, 
though  at  times  he  may  have  the  greatest  desire  to  break  from  it. 

GENERAL  SCIENCE  AND  RIGHT  LIVING 

Psychology  (sl-kol'o-ji)  deals  with  what  is  known  of  the 
activities  of  the  human  mind.  A  better  understanding  of  the 
conditions  for  these  activities  should  lead  to  a  better  intel- 
lectual and  moral  life.  It  is  necessary  that  the  psychologist 
know  very  definitely  the  structure  and  physiology  of  the 
brain  and  nervous  system  of  the  human  body,  and  be  well 
versed  in  biology.  But  it  is:neither  necessary  to  be  a  scien- 
tist, nor  to  have  gone  to  college,  in  order  to  know  the  condi- 
tions essential  for  growth  into  the  best  types  of  manhood 
and  womanhood. 

It  is  to  be  kept  in  mind  that  those  characteristics  which 
distinguish  mankind  from  the  brutes  are  the  result  of  a  slow 
process  of  human  development.  Education  through  schools 
has  to  do  with  this  development  of  intellectual  and  moral 
natures  in  individuals,  and  for  its  best  results  requires  time 
and  favorable  conditions.  While  schools  are  maintained  as 
one  of  the  chief  agencies  to  this  end,  it  must  be  remembered 
that  a  large  part  of  what  any  one  knows  and  is  able  to  do  has 
been  gained  outside  the  schoolroom. 

Influences  that  very  largely  shape  one's  choices  and  fix 
one's  ideals  of  life  are  those  of  the  home  and  its  surroundings 


HEALTH  AND  WELL-BEING  81 

during  childhood  and  youth.  Habits  of  thought  and  of 
action  formed  then  are  likely  to  control  in  later  life.  Self- 
indulgence  during  early  life  in  ways  and  manners  harmful 
to  the  individual  himself  and  offensive  to  others  gives  rise 
to  social  and  personal  limitations  during  the  later  years  of 
manhood  and  womanhood.  The  degree  of  self-control  and 
self-denial  learned  and  practised  during  youth  is  a  very  satis- 
factory measure  of  any  growth  towards  a  well  balanced 
complete  manhood  and  womanhood.  One  of  the  chief  ends 
of  school  attendance  is  to  acquire  ability  in  making  those 
choices  in  one's  manner  of  life,  and  in  all  matters  of  skill  and 
knowledge,  that  contribute  most  to  the  well-being  of  the  indi- 
vidual himself  and  of  other  people  generally. 

In  acquiring  information,  in  grasping  the  relationships 
of  facts,  and  in  making  applications  of  knowledge,  unless 
there  is  a  clear  discernment  on  the  one  hand  between  what  is 
for  the  well-being  of  the  individual  and  of  society,  and  on 
the  other  of  what  is  degrading  for  all,  the  purposes  of  schools 
may  be  largely  defeated.  The  development  of  an  intellec- 
tual and  moral  nature  in  an  individual  is  a  relatively  slow 
process  requiring  a  lifetime.  The  conditions  for  this  develop- 
ment are  in  large  part  within  the  control  of  the  individual 
himself.  It  is  his  own  choice  whether  his  educational  prog- 
ress shall  be  toward  the  formation  of  habits  that  experience 
and  science  have  shown  to  be  best,  or  toward  those  whose 
results  are  harmful  to  himself  and  to  others.  Enlightenment 
in  hygiene  and  sanitation,  and  in  the  ways  of  right  living 
generally,  assumes  that  every  one  who  is  at  all  reasonable 
and  sane  will  do  what  is  known  to  be  best,  and  avoid  doing 
what  is  either  questionable  or  absolutely  harmful. 

One  of  the  fundamental  facts  concerning  growth  from 
childhood  into  self-directing  manhood  or  womanhood  is  the 
gradual  assumption  of  responsibility,  and  a  manifest  readi- 
ness to  discharge  duties  without  compulsion.  Regardless 


82  GENERAL  SCIENCE 

of  one's  age  and  bodily  growth,  any  one  who  must  be  made  to 
do  what  he  ought  to  do,  and  who  must  be  compelled  to  refrain 
from  doing  what  is  wrong,  is  not  yet  grown.  He  is  yet  a 
child  in  the  ways  of  right  living.  As  persons  grow  older  in 
years,  and  come  to  some  degree  of  maturity  of  body,  it  is 
only  reasonable  that  their  conduct  should  give  evidence  of 
growth  into  the  better  types  of  manhood  or  womanhood. 
Knowledge  gained  in  schools  finds  its  chief  value  and  most 
fitting  expression  in  lives  that  are  guided  more  nearly  aright 
as  result  of  such  teachings. 

People  who  manifest  no  regard  for  the  welfare  and  rights 
of  others  may  very  properly  be  said  to  exhibit  criminal 
tendencies.  These  manifestations  range  all  the  way  from 
what  is  commonly  called  selfishness  to  that  utter  disregard 
which  does  not  hesitate  to  destroy  human  life  for  gain. 
Not  all  practices  included  in  such  a  sweeping  classification 
are  illegal  by  any  means,  i.e.,  prohibited  by  law.  The  liquor 
traffic  is  not  only  permitted  in  many  communities  but 
legally  authorized  by  license.  It  is  carried  on  regardless  of 
an  appalling  list  of  evils  that  result  from  it  both  public  and 
private.  The  adulterations  of  foodstuffs,  the  use  of  harm- 
ful preservatives,  and  the  traffic  in  habit-forming  drugs, 
have  been  made  illegal.  All  of  them  involve  the  robbing 
of  one  person  by  another  of  health,  of  ability  to  earn  a  liveli- 
hood, and  of  possibilities  for  advancement  in  general  welfare. 
In  individual  relationships  in  life  the  motto  "Quid  pro  quo," 
meaning  to  make  full  return  in  value  for  whatever  one  gets, 
is  conducive  both  to  manhood  and  to  good  citizenship. 

Activities  that  largely  control  the  development  of  the  body 
and  mind  occur  during  the  years  of  childhood  and  youth. 
There  is  lack  of  experience  then  concerning  the  wisdom  of 
what  ought  to  be  done.  Understanding  of  the  relationship 
of  cause  and  effect  in  matters  of  health,  and  of  the  conse- 
quences of  any  unwise  course  in  life,  comes  only  through  years 


HEALTH  AND  WELL-BEING  83 

of  experience  and  of  instruction.  The  age  of  discretion  and  of 
responsibility  in  conduct  is  slowly  attained.  The  experiences 
and  counsel  of  those  who  are  older,  whether  written  in  books, 
listened  to  at  home  or  in  school,  or  witnessed  in  lives  about 
us  that  are  worthy  of  being  followed  as  examples,  make  a 
wise  course  in  life  possible  until  personal  experience  can 
safely  modify  or  replace  these  safeguards.  Any  failure  to 
direct  one's  self  aright  does  not  destroy  all  growth  previously 
made  toward  manhood  or  womanhood.  Habits  are  the 
results  of  repeated  efforts,  and  the  importance  of  the  single 
act  as  explained  by  the  physiologist  and  the  psychologist 
lies  in  the  knowledge  that  another  like  act  becomes  more 
probable. 

SUMMARY 

The  larger  part  of  what  any  one  knows  is  learned  usually  outside 
school.  It  may  be  considered  that  the  chief  purpose  of  schools  is  to 
stimulate  and  direct  a  love  of  knowledge,  and  to  give  efficient  training 
in  its  acquisition  and  effective  use. 

What  has  been  learned  by  men  down  through  the  ages  in  any  one 
of  the  sciences  has  been  so  classified  and  related  that  it  is  possible  in 
a  year's  study  to  get  a  good  general  knowledge  of  it. 

Knowledge  becomes  of  largest  worth  when  it  promotes  our  own 
highest  welfare,  both  of  body  and  of  mind,  and  when  through  us  it 
benefits  others  in  largest  degree. 

Habits  of  any  kind  become  fixed  only  through  years  of  repetition. 
Both  the  training  and  the  instruction  given  in  schools  should  be  directly 
concerned  in  fitting  every  one  habitually  to  make  more  intelligent 
choices  in  his  manner  of  life,  and  in  all  matters  of  skill  and  of  knowledge. 

The  habits  formed  in  connection  with  doing  school  work  should  be 
such  as  to  make  men  and  women  more  efficient  in  life,  more  self-reliant, 
and  more  persistent  in  the  solution  of  life's  problems.  One's  whole 
life  should  be  more  sane  and  better  directed  by  reason  of  attendance 
upon  school. 

.  The  person  who  must  always  be  told  what  to  do  and  when  to  do  it, 
who  must  be  made  to  do  what  he  ought  to  do  and  made  to  refrain  from 
doing  what  he  ought  not  to  do,  is  not  yet  grown  up.  He  remains  a 
child  in  development  whatever  his  age  in  years  may  be. 


84  GENERAL  SCIENCE 

All  hope  of  the  progress  of  mankind,  and  one  of  the  chief  reasons 
for  maintaining  schools,  is  that  each  individual  and  each  generation 
in  turn  may  early  become  acquainted  with  the  gains  in  knowledge 
made  by  the  race.  This  renders  it  unnecessary  for  anyone  to  repeat 
the  mistakes  that  others  before  him  have  made. 

Many  of  the  evils  experienced  in  the  lives  of  people  are  the  direct 
results  of  wrong  habits  formed  before  the  full  significance  of  these 
habits  and  of  their  results  could  be  understood. 

Exercises 

1.  Explain  the  need  of  recreation  and  amusements.     What  unmistakably 
.distinguishes  them  from  dissipation? 

2.  Upon  what  set  ("system")  of  organs  of  the  body  does  any  narcotic 

(including  alcohol)  directly  act?     Explain  the  "stimulation"  '(increased 
activities)  from  the  use  of  small  portions  of  narcotics. 

3.  What  is  meant  by  the  drug  habit?     How  is  it  that  people  become  slaves 
to  it?     Why  is  the  habit  unlikely  to  be  overcome? 

4.  What  is  meant  by  "patent  medicines?"     Account  for  their  extended 
sales.     What  constitutes  sufficient  argument  against  their  use? 

6.  Name  some  of  the  conditions  a  person  must  observe  in  order  to  do  his 
best  and  be  at  his  best. 

6.  What  is  meant  by  a  sound  body?     Name  some  characteristics  commonly 
accepted  as  evidence  of  a  sane  mind. 

7.  What  is  understood  by  the  term  food,  whether  for  plants  or  for  animals? 

8.  Under  what  conditions  may  no  harm  come  from  being  up  late  nights? 
What  relationship  should  exist  between  one's  kind  of  recreation  and  the 
nature  of  his  employment? 

9.  Whence  is  derived  the  "life"  of  each  succeeding  generation  of  plants  and 
of  animals? 

10.  Why  may  it  be  well  to  abstain  from  eating  when  one  has  a  cold?     Why 

may  it  be  well  to  take  hot  drinks  and  a  vapor  bath  at  such  a  time? 

11.  What  constitutes  (a)  temperate  living;  (b)  a  "simple  life"? 

12.  What  should  be  the  great  service  performed  by  a  physician  for  his 

patients,  and  the  chief  aim  of  his  efforts?     What  has  been  found  true  of 
the  recuperative  powers  of  those  who  use  alcoholic  drinks? 

13.  What  only  can  medicine  do  for  the  restoration  of  wasted  energies  and 
a  broken-down  body? 

14.  In  human  society  when  must  a  person  be  prevented  by  others  from  doing 
as  he  pleases? 

15.  Give  illustrations  of  the  statement  that  those  who  will  not  deny  them- 
selves in  observing  nature's  laws  will  be  denied  by  her,  as  well  as  punished 
for  past  offenses. 


IV.  WATER,  AND  ITS  USES 
SOME  PROPERTIES  OF  WATER 

Water  is  indispensable  in  the  life  of  all  plants  and  animals. 
In  the  human  body  it  makes  possible  the  solution  (digestion) 
of  foods.  It  is  the  means  employed  in  the  body  for  removal 
of  waste  through  the  skin,  bowels,  and  kidneys.  It  keeps 
moist  the  tissues  so  that  they  can  perform  their  several 
functions.  In  Physics  a  study  is  made  of  water  as  a  type 
of  all  liquids.  In  Chemistry  both  its  physical  and  chemical 
properties  are  studied,  together  with  its  usefulness  in  pro- 
moting chemical  change  and  in  carrying  on  the  chemical 
processes.  In  the  study  of  Physical  Geography,  and  in 
Meteorology,  water  as  an  agent  in  the  changes  that  occur  is 
of  first  importance.  In  matters  of  hygiene  and  sanitation, 
and  in  the  affairs  of  the  household,  the  importance  of  water 
in  daily  life  can  scarcely  be  emphasized  sufficiently.  In  the 
affairs  of  men  and  of  nations  water  is  a  highway  for  foreign 
and  domestic  commerce,  while  water  and  steam  furnish  a 
large  part  of  the  power  that  turns  the  wheels  of  the  world 's 
industries.  Any  extended  consideration  of  its  usefulness 
to  individuals  and  to  mankind  generally  by  reason  of  its 
properties  and  its  abundance  leads  into  every  field  of  human 
activity.  . 

All  matter,  including  liquids  and  gases,  is  supposed  to  be 
made  up  of  minute  particles  called  molecules.  These  are 
too  small  to  be  seen  through  the  most  powerful  microscopes. 
It  is  further  supposed  that  these  molecules  as  units  of  matter 
are  separated  by  spaces  relatively  large  as  compared  with 
the  size  of  the  molecules  themselves.  And  it  is  believed  that 
these  molecules  are  incessantly  moving  back  and  forth  in 

85 


86  GENERAL  SCIENCE 

these  intermolecular  spaces  (pores),  and  that  the  degree  of 
this  motion  and  the  consequent  number  of  collisions  among 
the  molecules  is  the  cause  of  the  varying  temperatures  of 
bodies.  It  is  believed  that  the  distinctions  between  solids, 
liquids,  and  gases  lies  largely  in  the  different  intensities  of 
the  attractions  (pulls)  exerted  between  the  molecules  by  the 
intermolecular  forces  of  cohesion  and  adhesion.  In  solids 
the  attractive  forces  dominate,  and  the  solid  retains  a  form 
of  its  Own.  In  gases  the  moving  molecules  drive  one  another 
apart,  and  gaseous  matter  must  be  confined.  Left  unre- 
stricted, gases  would  expand  indefinitely  filling  all  space 
open  to  them.  Liquids  are  an  intermediate  condition  be- 
tween solids  and  gases,  and  possess  enough  of  freedom  in  the 
motion  of  their  molecules  to  assume  the  form  of  a  containing 
vessel.  Molecules  escape  from  their  upper  surfaces  into  the 
atmosphere  more  or  less  at  all  times  when  left  uncovered. 
The  rate  of  this  evaporation  varies  with  the  kind  of  liquid, 
its  temperature,  and  the  capacity  of  the  atmosphere  for 
holding  that  particular  vapor.  Many  liquids  are  said  to 
be  volatile  because  they  must  be  kept  in  stoppered  bottles 
or  other  containers  to  prevent  excessive  waste  due  to 
evaporation. 

Water  is  boiling  when  it  is  changing  to  a  vapor  within  the 
liquid  mass.  For  pure  water  under  one  atmosphere  of  pres- 
sure, .i.e.,  when  the  barometer  reading  is  thirty  inches  (76 
cm.),  the  boiling  temperature  is  100°  C.  (212°  F.).  When 
water  is  confined  in  a  closed  vessel,  as  in  the  boiler  of  a  loco- 
motive, and  the  gaseous  (steam)  pressure  upon  it  becomes 
more  and  more,  the  water  must  be  heated  hotter  and  hotter  to 
keep  it  boiling  as  the  pressure  upon  it  increases.  Under  two 
atmospheres  (thirty  pounds  per  square  inch)  the  boiling 
point  becomes  about  120°  C.,  and  at  fifteen  atmospheres 
becomes  about  200°  C.  If  at  any  such  high  temperature  the 
pressure  on  the  water  surface  be  suddenly  released,  the  heat 


WATER,  AND  ITS  USES  87 

contained  in  the  water  may  convert  the  whole  liquid  mass 
instantly  into  steam. 

By  use  of  " vacuum  pans"  having  air-tight  covers,  and 
with  a  pressure  upon  the  liquids  contained  in  them  kept  less 
than  one  atmosphere  by  use  of  an  exhaust  (air)  pump,  the 
boiling  may  go  on  rapidly  at  temperatures  much  below  100°  C. 
By  reason  of  a  lessened  atmospheric  pressure  due  to  increase 
in  altitude  the  boiling  point  of  water  is  lowered  about  one 
degree  in  temperature  for  approximately  1000  feet  elevation. 
At  Denver  one  mile  above  sea  level  the  boiling  point  is 
approximately  95°  C. 

In  the  use  of  rubber  bags  containing  hot  water  as  a  source 
of  warmth  through  a  period  of  several  hours,  we  have  an 
illustration  of  another  important  property  of  water.  Differ- 
ent bodies  having  the  same  weight  and  same  temperature 
give  off  widely  different  amounts  of  heat  in  cooling  through 
the  same  number  of  degrees.  This  is  another  way  of  saying 
that  the  same  amounts  of  heat  taken  up  by  equal  masses  of 
different  substances  having  the  same  initial  temperature 
give  widely  different  final  temperatures  to  these  masses. 

Water  has  the  highest  specific  heat  of  the  various  liquids 
and  solids.  Where  equal  weights  of  mercury  and  water  are 
heated  equally,  the  rise  in  temperature  of  the  mercury  is 
about  thirty  times  greater1.  Dry  land  surfaces  (soils)  heat 
much  faster  and  get  much  hotter  under  a  summer  sun  than 
bodies  of  water,  cooling  off  during  the  night  much  more 
rapidly  and  to  a  much  lower  temperature. 

A  cubic  foot  of  water  weighs  about  sixty-two  and  one-half 

!The  specific  heat  of  any  substance  may  be  defined  as  the  number  of  cal- 
ories of  heat  necessary  to  raise  the  temperature  of  one  gram  of  the  substance 
one  degree  centigrade.  The  specific  heat  of  water  is  i.oo  (see  page  147),  and 
the  specific  heat  values  of  the  following  substances  are  given  merely  for 
illustration: 

Mercury  (solid) 0.033         Aluminum  0.214 

Iron 0,113         Ice  0.550 


88  GENERAL  SCIENCE 

pounds.  In  freezing  it  expands  about  one-tenth  of  its 
volume,  and  a  cubic  foot  of  the  ice  that  is  formed  (not  the 
whole  of  the  cubic  foot  of  water)  weighs  about  fifty-seven 
pounds.  The  density  of  ice  is  about  nine-tenths  that  of 
water.  This  explains  why  ice  as  it  forms  on  the  surface  of 
water  in  winter  does  not  sink  to  the  bottom,  and  why  ponds 
and  streams  do  not  become  frozen  solid  during  a  winter. 
If  large  bodies  of  water  did  freeze  solid,  it  is  unlikely  that 
this  ice  would  ever  thaw  very  much  below  the  water  surface. 
The  heat  of  the  summer's  sun  upon  it  would  be  used  largely 
in  vaporizing  the  surface  layer  of  water.  All  marine  life 
would  be  destroyed,  and  the  waters  would  be  icy  cold  all 
summer.  Winds  blowing  over  this  ice  cold  water  would 
check  or  destroy  the  growth  of  vegetation.  With  the  den- 
sity of  ice  so  nearly  that  of  water,  it  is  calculated  that  about 
nine-tenths  (.92)  of  the  volume  of  an  iceberg  is  submerged 
however  much  it  towers  above  water  surface.  Within  a 
temperature  range  from  32°  to  212°  F.  (o°  to  100°  C.)  water 
exists  as  solid,  liquid,  and  vapor.  No  other  substance  has 
so  narrow  a  range  in  temperature  for  all  three  states. 

All  waters  coming  out  of  the  ground  are  likely  to  contain 
more  or  less  of  minerals  in  solution.  Inland  lakes  and  seas 
such  as  the  Great  Salt  Lake  of  Utah,  whose  waters  have  no 
outlet  other  than  by  evaporation,  become  increasingly 
saline  as  minerals  in  solution  are  washed  in  to  be  left  there. 
The  waters  of  the  ocean  contain  nearly  3  per  cent  of 
common  salt.  "  Mineral  springs"  contain  certain  dissolved 
compounds  that  have  more  or  less  of  medicinal  value. 
Usually  these  waters  as  sold  on  the  market  are  "  car- 
bonated, "  i.e.,  made  to  hold  under  pressure  considerable 
carbon  dioxide  gas.  When  this  water  is  poured  into  an 
open  glass,  and  is  under  only  the  ordinary  atmospheric 
pressure,  effervescence  occurs  by  reason  of  the  escape  of 
this  gas  into  the  air. 


WATER,  AND  ITS  USES  89 

Water  itself  is  practically  incompressible  even  under 
enormous  pressure.  Because  of  this  fact  the  density  of  the 
water  in  the  depths  of  the  ocean  is.  approximately  the  same 
as  at  the  surface.  Bodies  heavy  enough  to  sink  beneath  the 
surface  will  go  to  the  bottom.  This  incompressibility  of 
water  is  in  striking  contrast  with  the  ready  compressibility 
of  gaseous  matter  such  as  the  atmosphere. 

"Soda  water"  is  carbonated  drinking  water  sweetened 
and  flavored  by  use  of  fruit  syrups.  Substances  chemically 
prepared,  and  having  flavors  similar  to  those  of  various 
fruits,  are  sometimes  used  in  place  of  the  real  fruit  because 
of  cheapness.  Their  use  may  be  attended  with  harmful 
results,  especially  for  those  whose  digestion  is  at  all  impaired. 

SUMMARY 

The  important  uses  of  water  are  too  numerous  to  be  named  here. 
Very  many  of  these  uses  are  named  elsewhere  in  this  text  in  different 
connections.  In  agricultural,  commercial,  and  industrial  life,  and  in 
all  relations  of  life  affecting  health  and  well-being,  water  occupies  a 
most  important  place. 

A  detailed  study  of  water  as  a  typical  liquid  is  made  in  Physics. 
Brief  studies  of  other  liquids  can  then  be  made  by  comparison.  Its 
composition,  and  its  usefulness  in  chemical  changes,  are  both  empha- 
sized in  Chemistry,  while  in  the  other  sciences  the  uses  of  water  appear 
in  manifold  relationships. 

The  boiling  and  freezing  temperatures  vary  for  different  liquids 
These  temperatures  are  changed  for  any  liquid  by  variations  in  atmos- 
pheric pressure,  and  by  the  presence  or  absence  of  substances  in 
solution. 

The  high  specific  heat  of  water,  and  the  excessive  value  of  the  heat 
involved  in  its  vaporization,  are  of  utmost  importance  in  any  con- 
sideration of  climate. 

Abundant  as  are  the  waters  of  earth,  it  is  a  most  difficult  problem  to 
secure  a  supply  of  water  sufficiently  free  of  organic  and  mineral  matter, 
and  of  disease  germs,  to  warrant  its  use  for  household  purposes. 
Oceanic  waters,  and  those  of  certain  inland  lakes,  seas,  and  springs, 
hold  in  solution  so  much  salt,  "lime,"  and  other  minerals  as  to  be 
unfit  for  drink  and  for  the  preparation  of  foods. 


90  GENERAL  SCIENCE 

Water  can  hold  gases  as  well  as  solids  in  solution.  Both  marine 
and  land  plants  get  the  needed  supply  of  oxygen  for  their  tissues  from 
the  water.  Fish  are  provided  with  special  organs  known  as  gills  to 
get  from  the  water  that  passes  in  and  over  them  the  oxygen  they 
require.  When  water  containing  any  gas  is  freed  from  pressure,  more 
or  less  of  the  dissolved  gas  will  escape.  This  is  seen  in  "soda  water," 
and  in  all  carbonated  mineral  waters. 

VAPORIZATION  AND  CONDENSATION 

As  elevation  above  the  earth's  surface  increases  it  is  found 
that  the  pressure  exerted  by  the  atmosphere  decreases.  In 
the  study  of  Physics  it  is  also  found  that  when  the  pressure 
upon  any  gas  is  decreased  the  gas  not  only  expands  but  its 
temperature  falls.  This  result  follows  from  the  molecules 
being  further  apart.  As  atmospheric  moisture  rises  in  the 
form  of  invisible  vapor  of  water  it  expands  and  cools,  and  the 
formation  of  clouds  with  or  without  rain  or  snow  may  follow. 
The  air  may  cool,  also,  by  reason  of  radiation  of  its  heat  out 
into  space  independent  of  any  expansion. 

Clouds  and  fogs,  consist  of  minute  droplets  of  water  as  a 
liquid.  These  cloud  masses  of  water  particles  are  heavier 
than  air,  and  are  all  the  time  settling  toward  the  earth's 
surface.  Where  the  under  surfaces  of  the  cloud  mass  come 
in  contact  with  warmer  air,  or  air  that  is  unsaturated,  the 
liquid  particles  change  back  into  the  vapor  form.  But 
while  the  cloud  is  thus  wasting  below,  it  may  be  forming 
anew  elsewhere,  especially  at  the  upper  surfaces.  Thus 
the  form  of  the  cloud  is  more  or  less  constant. 

The  amount  of  rainfall  in  some  of  the  regions  of  earth  is  a 
negligible  quantity,  while  the  amazing  total  of  500  inches  or 
over  forty  feet  a  year  is  recorded  for  the  region  northeast 
of  the  Bay  of  Bengal.  Where  the  annual  rainfall  is  under 
twenty  inches,  the  raising  of  crops  without  irrigation  is 
hazardous.  The  distribution  of  the  rainfall  through  ^the 
growing  season  is  a  factor  quite  as  important  as  the  matter 


WATER,  AND  ITS  USES 


92  GENERAL  SCIENCE 

of  a  few  inches  more  or  less  annually.  In  the  region  just 
east  of  the  Rocky  Mountains  the  rainfall  is  deficient,  and 
just  east  of  the  Sierra  Nevadas  in  Nevada,  Utah,  and  adja- 
cent regions,  it  is  scarcely  five  inches  a  year.  On  the  north 
Pacific  Coast  of  the  United  States  the  rainfall  is  about 
seventy  inches  per  year. 

AVater  vapor  when  cooled  rapidly  and  to  a  sufficiently  low 
temperature  forms  beautiful  crystals  known  as  frost.  These 
may  gather  on  window  panes  and  other  exposed  surfaces,  or 
may  float  about  in  the  air.  Snow  flakes  may  be  considered 
as  masses  of  frost  crystals.  Ice  and  snow  and  frost  form  at 
temperatures  below  32°  F.  (o°  C.),  and  melt  when  above  this 
"freezing  point."  Ice  melts  at  32°  F.  as  heat  is  added  to  it, 
and  water  at  32°  F.  freezes  as  heat  is  abstracted  from  it.  It 
must  be  remembered,  however,  that  vaporization  of  water 
occurs  at  any  temperature  even  from  the  frozen  (solid)  state. 

When  melted  iron  is  run  into  moulds,  it  is  found  when 
solidified  to  have  increased  enough  in  volume  to  take  any 
markings  that  may  have  been  on  the  sides  of  the  mould. 
Iron  and  steel  castings  are  made  in  this  way,  and  any  desired 
patterns  may  be  had  upon  their  surfaces.  When  cast  iron 
is  broken  a  crystalline  structure  is  easily  noted  by  use  of  a 
magnifying  glass.  The  increase  in  volume  is  explained  by 
the  added  space  required  for  the  newly  formed  crystals 
whose  regular  forms  do  not  fit  as  closely  together  as  did  their 
molecules  before  the  crystals  formed.  The  change  of  water 
to  ice  is  similar,  and  experiences  with  broken  pipes  are 
common  when  water  is  allowed  to  freeze  in  them.  A  block 
of  ice  is  just  a  mass  of  more  or  less  perfectly  formed  crystals 
indistinguishable  save  when  they  are  forming  or  when  they 
fall  apart  as  the  ice  "honey-combs." 

The  process  of  vaporizing  solids,  and  then  condensing  the 
vapor  to  the  solid  state  once  more  without  passing  through 
the  liquid  state  in  either  case,  is  called  sublimation.  The 


WATER,  AND  ITS  USES  93 

solid  that  has  thus  passed  through  both  changes  is  a  subli- 
mate. Distillation  is  the  vaporization  of  a  liquid  and  the 
condensation  of  this  vapor  back  to  a  liquid  state  again. 

Air  containing  much  moisture  does  not  allow  heat  to  pass 
through  it  readily.  When  a  cloud  passes  between  an  ob- 
server and  the  sun  on  a  hot  day  in  summer  the  relief  due  to 
absorption  of  the  sun's  heat  within  the  cloud  mass  is  very 
noticeable. 

Not  only  does  the  total  amount  of  water  per  cubic 
foot  in  the  air  vary  at  different  times,  but  the  capacity  of  the 
air  for  holding  water  vapor  varies  widely  with  changes  in  its 
temperature.  The  ratio  of  the  amount  of  water  vapor  pres- 
ent in  the  air  at  any  time  to  the  amount  that  the  air  might 
then  hold  is  known  as  relative  humidity.  It  tells  what  per 
cent  saturated  the  air  is  at  that  time.  Air  is  saturated  when 
the  humidity  is  100  per  cent. 


Grams  of  water  vapor  per 
saturated  cub' c  meter. 


-J°  0°  5'  10°          15°         £0 

Tempera  ture    Centigrade 


FIG.  33. — Capacity  of  the  air  for  moisture  at  different  temperatures,    j 

SUMMARY 

The  invisible  water  vapor  in  the  atmosphere  when  cooled  sufficiently 
is  changed  back  into  the  liquid  state.  This  cooling  may  result  from 
incoming  cold  air  as  a  cold  wind,  or  it  may  occur  when  the  moisture- 
laden  air  rises  and  mixes  with  air  in  the  upper  colder  levels  of  the 
atmosphere.  Then,  too,  cooling  may  be  the  direct  result  of  expansion 
of  air  containing  water  vapor  as  it  rises  where  the  pressure  upon  it 
becomes  less  and  less. 


94  GENERAL  SCIENCE 

The  cloud  masses  consist  of  minute  droplets  of  water  which  are  con- 
tinuously settling  toward  the  earth.  While  in  a  general  way  their 
forms  persist,  clouds  are  all  the  time  undergoing  change  by  wasting 
at  the  lower  surfaces  and  by  reforming  higher  up. 

When  the  temperature  of  the  air  falls  below  freezing,  the  water 
vapor  it  contains  may  be  changed  to  frost  crystals.  Masses  of  these 
crystals  form  snowflakes.  When  the  ground,  the  roofs  of  buildings, 
and  other  surfaces  are  below  freezing  temperature,  and  the  air  is 
warmer  and  moisture-laden,  frost  is  likely  to  form  upon  the  cold 
surfaces. 

The  presence  of  water  in  the  air,  whether  as  vapor  or  as  cloud  par- 
ticles, serves  more  or  less  as  a  blanket,  and  lessens  the  rate  of  xrooling 
of  the  earth's  surface  at  night. 

As  the  air  cools  at  night  its  capacity  for  holding  moisture  decreases. 
With  the  same  amount  of  vapor  of  water  present  in  the  air,  its  relative 
humidity  or  per  cent  of  saturation  increases.  In  the  early  evening 
this  increase  is  often  rapid. 

Condensation  is  the  opposite  of  vaporization,  and  both  processes 
are  involved  in  distillation.  Natural  distillation,  with  the  sun 
as  source  of  the  heat,  plays  a  large  and  important  part  in  weather  con- 
ditions. The  rainfall  of  any  region  that  is  destitute  of  large  water 
surfaces  is  dependent  in  great  part  upon  winds  blowing  from  other 
regions  where  vaporization  is  abundant.  These  winds,  if  unduly  con- 
tinued, result  in  a  wet  season  for  inland  areas,  while  their  deflection  or 
cessation  for  causes  unknown  accounts  for  a  dry  season. 

HEAT  OF  VAPORIZATION,  AND  OF  FUSION 

It  has  been  found  that  to  change  the  temperature  of  one 
pound  of  water  one  degree  on  the  Fahrenheit  thermometer 
always  involves  the  same  amount  of  heat.  It  makes  no 
difference  whether  the  water  is  warmed  or  cooled.  This 
quantity  of  heat  is  used  as  the  unit  in  computation  of  heat 
values,  and  is  known  as  the  British  thermal  unit.  Then 
if  water  weighing  twelve  ounces  (three-fourths  pound)  has  its 
temperature  raised  6J^°  F.,  the  water  has  gained  %  X  6^, 
or  4%  British  thermal  units. 

Most  science  texts  make  use  of  the  metric  system  of 
weights  and  measures.  It  is  much  more  simple  to  learn 


WATER,  AND  ITS  USES  95 

and  to  use,  and  its  general  adoption  in  business  and  in 
schools  is  desirable.  Its  heat  unit  is  called  the  calorie, 
and  its  value  is  the  heat  involved  in  changing  the  temperature 
of  one  gram  of  water  one  degree  of  the  Centigrade 
thermometer. 

It  has  been  found  by  repeated  experiments,  carefully 
conducted  in  physics  laboratories,  that  when  ice  melts 
about  79  calories  of  heat  disappear  for  every  one  gram 
melted.  In  other  words  the  heat  of  fusion  of  ice  is 
79  calories  per  gram.  In  similar  experiments  the  heat 
of  vaporization  is  found  to  be  about  536  calories  per 
gram  of  water. 

The  meaning  of  these  values  is  somewhat  difficult  to 
grasp  at  first.  Let  it  be  illustrated  in  this  way.  To  cool 
boiling  hot  water  (100°  C.)  down  to  the  freezing  temperature 
(o°  C.)  involves  the  liberation  of  100  calories  of  heat  per  gram. 
If  that  same  one  gram  of  water  at  o°  C.  is  changed  to  ice  at 
o°  C.,  involving  a  change  of  state  from  liquid  to  solid  but  no 
change  in  temperature,  almost  80  calories  of  additional  heat 
are  liberated — the  heat  that  was  required  to  keep  the  gram  of 
ice  in  the  liquid  state. 

Even  more  striking  is  the  meaning  of  the  536  calories  of 
heat  of  vaporization  of  water.  In  the  condensation  of 
invisible  water  vapor1  whose  temperature  is  100°  C.  to  water 
that  is  boiling  hot  (100°  C.),  involving  as  it  does  a  change 
of  state  without  change  of  thermometer  readings,  there  is 
5.36  times  as  much  heat  set  free  as  when  that  same  water 
is  cooled  from  its  boiling  temperature  to  the  freezing 
temperature. 

A  common  use  of  the  great  heat  value  of  this  " latent  heat" 
of  steam  is  in  the  warming  of.  rooms  and  buildings  by  the 
condensation  of  relatively  small  weights  of  steam  in  radia- 

1  The  so-called  steam  that  is  visible  consists  of  a  cloud  of  minute  water 
particles  resulting  from  the  condensation  of  invisible  water  vapor. 


96  GENERAL  SCIENCE 

tors.     These  are  connected  by  means  of  pipes  with  boilers 
that  are  often  located  at  considerable  distances  away. 

It  is,  however,  in  the  study  of  Physical  Geography,  and  of 
Meteorology,  that  one  comes  to  have  some  true  notion  of  the 
vast  scale  upon  which  heat  is  made  "latent"  in  the  vaporiza- 
tion of  enormous  quantities  of  water  by  the  sun,  and  then 
later  set  free  as  this  water  vapor  condenses.  These  changes 
are  going  on  everywhere  over  the  earth,  but  on  the  largest 
scale  in  the  tropical  regions.  Our  weather,  and  the  intensity 
of  storms,  are  both  directly  related  to  the  heat  values  in- 
volved in  these  changes  in  the  state  of  water.  It  will  be 
necessary  to  keep  in  mind  that  other  substances  than  water 
exhibit  like  phenomena,  and  that  the  value  in  calories  of 
their  heat  of  fusion  and  their  heat  of  vaporization  varies 
with  the  substance. 

SUMMARY 

Heat  like  other  forms  of  energy  can  be  measured.  The  units  em- 
ployed for  this  measurement  are  the  calorie,  and  the  British  thermal 
unit. 

There  is  a  wide  variation  in  the  amounts  of  heat  required  to  melt 
equal  weights  of  different  solids,  and  to  vaporize  equal  weights  of  dif- 
ferent liquids.  The  heat  of  fusion  for  water  in  the  form  of  ice  is  79 
calories  per  gram,  and  for  its  vaporization  from  the  liquid  state  is  536 
calories  per  gram. 

The  heat  used  in  changing  water  as  a  liquid  into  vapor,  whether  on 
the  stupendous  scale  of  natural  vaporization  or  in  steam-heating  plants 
or  elsewhere,  is  wholly  set  free  when  condensation  of  the  vapor  occurs. 

To  continue  wearing  damp  or  wet  clothing,  and  to  allow  it  to  dry 
out  while  being  worn,  involves  the  abstraction  of  much  heat  from  the 
body.  This  loss  of  heat  ordinarily  can  ill  be  afforded. 

Soils  containing  water  will  absorb  large  amounts  of  heat  with  small 
rise  in  their  temperature.  This  is  by  reason  of  the  high  specific  heat 
of  water.  Then,  too,  by  reason  of  the  extremely  large  value  for  the 
heat  of  vaporization  of  water,  soils  that  are  water  soaked  are  likely  to 
remain  cold  and  unfit  for  plant  growth  late  into  the  Spring,  and  after 
periods  of  wet  weather.  Soils  with  good  drainage  warm  much  more 
rapidly. 


WATER,  AND  ITS  USES  97 

Exercises 

1.  When  persons  climb  mountains,  or  go  up  into  the  clouds  in  balloons, 
what  are  the  clouds  found  to  be? 

2.  Why  does  not  all  the  water  of  the  atmosphere  fall  to  earth  (a)  when  it 
is  in  vapor  (gaseous)  form;  (b)  when  in  minute  droplets  as  in  fog? 

3.  Why  is  it  that  in  winter  we  sometimes  can  "see  our  breath?" 

4.  Explain  the  thinning  out  and  disappearance  of  the  clouds  of  early  morn- 
ing as  the  sun  rises  higher  and  higher.     Why  is  it  that  at  other  times  as 
rain  continues  the  clouds  break  away  giving  place  to  clear  skies? 

6.  Whenever  there  is  an  inch  of  rainfall,  (a)  what  is  the  number  of  cubic 
feet  of  water  that  falls  per  acre  of  land;  (6)  how  many  gallons  (231  cubic 
inches  =  one  gallon) ;  (c)  how  many  tons  (one  cubic  foot  =  62.4  pounds)  ? 

6.  Name  and  describe  several  forms  of  clouds. 

7.  Aside  from  rainfall,  what  important  part  in  nature  is  served  by  clouds? 

8.  How  may  an  ample  supply  of  water  for  drink  and  for  cooking  purposes 
be  provided  on  long  journeys  by  ship?    In  what  way  may  a  supply  of 
ice  be  provided? 

9.  What  is  meant  by  "humidity"  of  the  atmosphere?     What  is  the  exact 
significance  of  the  term  "relative  humidity?" 

10.  Whence  comes  the  heat,  directly  or  indirectly,  for  natural  distillation? 

11.  Be  ready  to  quote  and  interpret  the  last  stanzas  of  Longfellow's  Rain 
In  Summer. 

12.  What  may  explain  in  part  the  refreshing  coolness  that  frequently  follows 
a  summer  shower?     What  relation  is  there  between  the  temperature  of 
soil  under  a  summer  sun  and  the  abundance  of  water  in  it?     Why  is 
this  so? 

13.  Explain  the  heating  of  rooms  and  buildings  by  steam  as  a  phenomenon 
of  heat  of  vaporization.     What  is  true  of  the  temperature  of  water  boiling 
freely  in  a  tea-kettle  as  it  is  heated  more  and  more?     Explain. 

14.  Explain  how  the  melting  of  ice  and  snow,  and  of  the  frost  in  the  ground, 
delays  the  coming  of  warm  weather  in  spring  time. 

15.  What  is  meant  by  the  heat  of  fusion?     Describe  an  experiment  to  explain 
it. 

16.  What  is  a  calorie?     What  is  the  value  in  calories  of  the  latent  heat  (a)  of 
steam;  (6)  of  ice? 

17.  What  is  the  part  played  by  moisture  in  the  atmosphere  in  equalizing 

throughout  the  year  the  temperatures  of  coast  regions?     Account  for 
the  extremes  of  temperature  of  inland  arid  districts  by  day  and  by  night. 

SOLUTION,  DIFFUSION,  ABSORPTION,  AND  OSMOSIS 

The    phenomena   of   absorption,   diffusion,   solution,  and 
osmosis  are  easily  understood  on  the  hypothesis  that  a  chief 


98 


GENERAL  SCIENCE 


NH. 


difference  between  the  solid,  liquid,  and  gaseous  forms  of 
a  body  is  in  their  rate  of  molecular  movements,  and  in  the 
size  of  the  spaces  (" pores")  between  the  molecules.  An 
hypothesis  in  science  is  a  supposition  used  as  an  explanation 
of  phenomena.  Systematic  advance  in  scientific  knowledge 
makes  large  use  of  hypotheses.  It  must  always  be  remem- 
bered, however,  that  these  hypotheses  are  based  upon  what 
is  known  to  be  true,  and  that  they  are  always  subject  to  change 
to  accord  with  any  newly  discovered  facts. 
A  belief  found  to  have  wide  application,  and  always  found 

true  to  the  facts  of  the 
natural  world  wherever  it 
is  applicable,  is  known  as 
a  "law"  in  science.  It 

••••j  j  I    (<jas)     may  be   noted   here  that 

\Jas)  /   \^  X   V.  civil  and  military  laws  on 

the  other  hand  are  re- 
quirements that  certain 

Fir,   34.-Diffusion  of  gases.  named      thingS       sha11      be 

done  or  shall  not  be  done. 

The  penalty  for  disregard  of  any  of  nature's  laws  is  not 
imposed  by  any  court  or  judge.  It  follows  as  a  natural 
consequence  of  failure  to  observe  them.  This  is  just  as  true 
when  ignorance  occasions  the  offense  as  when  done  wilfully 
and  by  design. 

When  like  states  of  matter  intermingle  by  reason  of  their 
own  molecular  activities,  the  change  (phenomenon)  is  called 
diffusion.  Owing  to  the  relatively  strong  attraction  be- 
tween the  molecules  of  solids  scarcely  any  diffusion  takes 
place  between  them  at  ordinary  temperatures  even  when 
in  close  contact.  When  molecules  of  unlike  states  of  matter 
intermingle  the  phenomenon  is  called  absorption.  If  as 
result  of  either  absorption  or  diffusion  a  homogeneous  (ho- 
mo-ge'ne-iis)  liquid  results,  the  term  solution  is  preferred 


WATER,  AND  ITS  USES  99 

to  either  of  the  others.  When  diffusion  of  liquids  or  diffu- 
sion of  gases  occurs  through  a  porous  (permeable)  partition, 
the  phenomenon  is  called  osmosis. 

To  change  a  solid  to  the  liquid  state  requires  an  expendi- 
ture of  heat.  This  is  manifestly  the  case  in  the  melting 
of  ice,  and  of  such  substances  as  sulphur  or  lead.  As  salt 
dissolves  in  water  there  may  be  a  noticeable  fall  in  the 
temperature  of  the  liquid.  Heat  is  abstracted  from  the 
water  to  aid  in  changing  the  salt  to  a  solution.  When  salt 
has  been  scattered  over  ice  that  has  been  broken  into  small 
lumps  the  surfaces  of  which  are  water  covered,  the  lumps  may 
become  frozen  together.  This  is  because  the  heat  abstracted 
from  the  ice  cold  water  as  the  salt  dissolves  is  sufficient  to 
convert  the  water  into  ice.  In  the  freezing  of  ice  cream  the 
heat  lost  by  the  cream  is  partly  used  in  the  solution  of  the 
salt  to  form  a  brine,  but  more  largely  in  the  melting  of  the 
ice  packed  around  the  can  that  contains  the  cream. 

The  boiling  temperature  of  the  solution  of  any  solid  in 
water  is  higher,  and  its  freezing  temperature  is  lower,  than 
with  pure  water.  A  saturated  solution  of  common  salt,  for 
example,  does  not  freeze  until  the  temperature  reaches 
-22°  C.  Advantage  is  taken  of  this  fact  in  making  ice 
cream,  and  in  the  use  of  solutions  of  calcium  chloride  or  of 
common  salt  (sodium  chloride)  for  the  brine  into  which  the 
cans  of  pure  water  are  set  in  making  artificial  ice.  The 
waters  of  sheltered  inlets  of  the  ocean  may  remain  open  in 
winter,  when  near  by  fresh  waters  in  rivers  and  lakes  become 
ice  covered. 

Osmosis  in  plants  and  animals  is  a  phenomenon  of  utmost 
importance.  The  circulating  fluid  in  both  cases,  containing 
as  it  does  the  dissolved  food  material,  must  penetrate  all 
parts  of  the  tissues  and  make  available  to  every  living 
cell  the  nourishment  it  needs. 

The  less  dense  any  solution  or  gas  is  the  more  likely  it  is 


100 


GENERAL  SCIENCE 


to  pass  rapidly  through  a  porous  partition.  Where  liquids 
or  gases  upon  opposite  sides  of  a  partition  are  of  different 
densities,  the  more  rapid  inflow  of  the  less  dense  fluid  causes 
a  pressure  within.  Though  the  rise  of  water  through  the 
stems  of  plants,  even  to  the  very  tops  of  the  giants  of  the 

redwood  groves  of  the  Pacific 
Coast,  may  not  be  wholly  un- 
derstood, this  osmotic  pressure  is 
in  part  an  explanation  of  it.  The 
height  of  the  liquid  column  in 
an  experiment  with  a  diffusion 
bulb  measures  the  large  pressure 
developed  there.  Plants  at  times 
do  not  have  a  sufficient  supply 
of  water  in  hot  summer  days  to 
make  good  their  loss  through  the 
leaves.  If  the  inflow  of  sap  into 
the  cells  of  a  plant  is  insufficient 
to  keep  them  filled,  the  plant  wilts 
until  such  time  as  these  conditions 
change.  The  term  osmosis  implies 
interchange  of  like  fluid  states 
through  a  porous  partition,  as 
liquid  mixing  with  liquid  or  gas 
mixing  with  gas.  However,  some 
liquids  osmose  so  very  slowly  that 

their  passage  through  the  membrane  becomes  a  negligible 
quantity,  and  the  flow  becomes  practically  a  mass  movement 
of  one  of  the  fluids  in  one  direction  only. 


FIG.  35. — Osmosis.  The  more 
rapid  inflow  of  liquid  from  A 
to  B  has  elevated  the  liquid 
surface  within  from  b  to  a. 


SUMMARY 

Where  like  states  of  matter  intermingle  by  reason  of  their  molecular 
movements  alone,  as  in  the  mixing  of  two  free  gases,  the  change  is 
known  as  diffusion.  Where  the  states  of  matter  are  unlike,  as  ink  into 


WATER,  AND  ITS  USES^  ,  ,         101 

a  blotter  or  air  into  water,  the  phenomenon  is  called  absorption.  If 
the  result  of  the  diffusion  or  absorption  is  a  homogeneous  liquid,  the 
phenomenon  is  preferably  called  solution.  Freedom  of  the  molecules 
to  intermingle  is  common  in  all  these  phenomena. 

In  science  a  formal  statement  of  a  general  truth  of  wide  application 
is  known  as  a  law.  To  the  extent  to  which  a  law  is  applicable  its  state- 
ments must  always  be  in  accord  with  the  facts  of  any  particular  case. 

An  hypothesis  is  a  supposition  advanced  to  give  a  clearer  under- 
standing of  any  phenomenon,  or  any  group  of  closely  related  phe- 
nomena. It  is  always  subject  to  change  as  additional  information  con- 
cerning these  phenomena  is  acquired,  but  it  is  always  based  upon  what 
is  known  to  be  true. 

Where  the  diffusion  of  like  states  of  matter  takes  place  through  a 
porous  partition,  as  when  the  liquids  within  and  without  the  cells  in 
plants  and  in  animals  intermingle,  the  phenomenon  is  known  as  os- 
mosis. The  less  dense  a  gas  is,  or  the  less  dense  a  liquid  is,  the  more 
rapidly  it  gets  through.  By  reason  of  an  unequal  rate  of  diffusion 
through  porous  partitions  there  is  developed  what  is  called  an  osmotic 
pressure  of  varying  value. 

Some  substances  such  as  white  of  egg,  glue,  and  cooked  starch, 
osmose  very  slowly  if  at  all  even  as  thin  liquids.  They  are  known  as 
colloids. 

Exercises 

1.  Give  several  illustrations  of  the  phenomena  (a)  of  diffusion;  (b)  of  absorp- 
tion.    In  which  of  these  cases,  if  any,  is  there  also  a  solution?     Why  so? 

2.  What  length  of  time  can  man  go  without  water  and  (a)  not  suffer;  (6)  not 
die?     With  abundance  of  water  all  about  them  why  do  men  die  of  thirst 
at  sea? 

3.  Why  is  the  "lime"  in  waters  used  as  drink  and  in  cooking  likely  to  be 
harmful  to  the  body?     Name  some  of  the  grains  which  as  foodstuffs 
are  chief  sources  of  supply  of  bone  material. 

4.  What  is  meant  by  the  phenomenon  of  osmosis  ?     How  is  it  to  be  accounted 
for?     Explain  osmotic  pressure. 

5.  That  osmosis  may  go  on  freely  throughout  the  body  what  must  be  true 

of  the  condition  of  the  tissues?     What  is  meant  by  (a)  the  lymph;  (6) 
the  lymphatic  (lim-fat'-ik)  system  of  the  body? 

6.  Since  the  starchy  foods  from  plants,  and  albuminous  foods  like  white 
of  egg,  do  not  when  in  solution  osmose  readily,  what  change  is  necessary 
during  digestion  besides  just  dissolving  them? 


102  GENERAL  SCIENCE 

• 

STREAMS,  VALLEY  FORMATION,  AND  SURFACE  EROSION 

Into  the  lives  of  those  whose  childhood  days  are  spent 
near  beautiful  rivers  or  smaller  streams  there  comes  much 
of  pleasure  and  of  education  denied  to  others  less  happily 
situated.  Aside  from  the  sports  of  fishing,  rowing,  skating, 
and  swimming,  the  variations  in  surface  forms  that  are  an 


FIG.  36. — A  stream  in  mid- winter. 

accompaniment  of  such  streams  enrich  the  experiences  of 
life,  and  make  possible  a  clearer  understanding  of  the  geo- 
graphic and  economic  conditions  of  other  regions  of  the  earth. 
There  will  be  a  variety  in  the  landscape  due  to  differences 
in  land  elevations,  and  the  occupations  of  the  people  will  be 
varied  because  of  the  different  natural  conditions  existing 
in  a  region  of  irregular  surfaces. 

Any  study  of  the  history  of  the  United  States  goes  hand 


WATER,  AND  ITS  USES  103 

in  hand  with  a  knowledge  of  its  geography.  Its  navigable 
streams  have  affected  in  large  measure  the  trade  and  indus- 
tries of  the  country,  and  the  location  of  its  large  cities. 
Until  the  advent  of  railways,  these  streams  were  the  chief 
factors  in  determining  the  directions  of  development  of  the 
country.  By  reason  of  a  full  knowledge  of  the  streams  of 
one's  own  locality,  and  of  their  relationship  to  local  affairs, 
there  is  made  possible  a  better  understanding  of  the  geog- 
raphy and  history  of  the  state  and  nation,  and  of  the  more 
distant  parts  of  the  earth. 

From  a  careful  study  of  any  good  map  of  one's  own  county 
or  township1,  it  becomes  possible  by  noting  the  direction  of 
flow  of  its  streams,  to  determine  among  other  things  (a) 
where  the  highest  lands  are  located;  (b)  what  apparently 
influenced  the  location  of  the  older  settlements  known  to 
have  been  made;  (c)  how  railroads  have  affected  the  growth 
of  towns  in  the  region  studied;  (d)  what  becomes  of  the 
waters  flowing  out  from  that  region;  (e)  the  probable  use 
made  of  the  streams  for  trade  and  industry. 

A  study  of  the  streams  of  any  section,  including  their 
rate  of  current  and  volume  of  flow,  the  character  of '  the 
banks  and  the  beds  of  these  streams,  contributes  much  to  an 
accurate  knowledge  of  the  region  in  which  one  lives.  Closely 
associated  with  this  should  be  a  knowledge  of  the  character 
of  the  soils,  of  the  natural  and  industrial  resources  of  that 
section,  and  of  how  its  prosperity  is  related  to  all  these. 

One  of  the  most  extensive  wastes  of  natural  wealth  and 
resources  in  the  United  States  during  the  last  half  of  the 
nineteenth  century  was  that  of  fertile  soil  from  the  surface 
layers  of  its  landed  areas.  Extensive  forests  covering  a  large 
portion  of  the  country  were  cut  away,  and  as  a  direct  result 
of  deforestation  enormous  waste  by  erosion  went  on  year  after 
year.  Following  the  breaking  up  of  the  sod  covering  of  the 
1  If  neither  is  at  hand  make  use  of  the  largest  available  map  of  the  State. 


104 


GENERAL  SCIENCE 


FIG.  37. — An  eroded  surface.     (Courtesy  U.  S.  Forest  Service.) 


WATER,  AND  ITS  USES  105 

fertile  loam  soils  of  the  central  portions  of  the  country, 
products  of  the  decay  of  vegetation  through  long  periods  of 
time  were  washed  away  from  the  surface  slopes. 

As  direct  result  of  ill-advised  methods  of  cultivation  of  these 
slopes,  not  only  were  they  denuded  of  their  best  soil  but  they 
became  gullied  and  worthless  as  tillable  land.  Proper  con- 
servation through  tillage  and  general  management  might 
have  kept  these  lands  productive  for  all  time.  Rivers  like 
the  Missouri  and  the  Mississippi  have  their  waters  laden  with 
soil  washed  from  the  land  surfaces  within  their  basins,  and 
this  earth  material  is  almost  wholly  lost  as  available 
productive  soil1.  A  similar  process  continued  through  longer 
periods  has  resulted  in  some  parts  of  the  world,  such  as 
northern  China,  in  large  areas  unfit  for  tillage  and  for  all 
agricultural  pursuits.  Though  large  areas  of  productive  lands 
are  being  brought  into  use  by  irrigation  in  the  arid  sections  of 
the  country,  the  annual  losses  by  erosion  of  tillable  lands,  and 
the  washing  away  of  their  most  fertile  parts,  represents  a 
deplorable  waste  of  the  wealth  of  the  nation.  So  dependent  is 
the  present  prosperity  and  the  future  greatness  of  any  people 
or  nation  upon  the  productiveness  of  the  soil  that  its  impover- 
ishment rather  than  its  betterment  is  a  national  calamity.  In 
1902  the  Reclamation  Act  was  passed  by  Congress  authorizing 
large  outlays  for  irrigation  systems  in  the  arid  regions  of  the 
United  States.  These  undertakings  have  involved  the  build- 
ing of  great  dams  for  storage  of  waters  and  the  construction 
of  water  channels.  In  Colorado,  water  from  the  Gunnison 
River  is  made  to  flow  through  a  long  tunnel  to  irrigate  the  ad- 
joining valley.  The  sale  of  "water  rights"  on  irrigated  lands 
is  expected  in  time  to  return  to  the  government  all  the 
outlays  made. 

1  It  has  been  estimated  (Salisbury)  that  the  amount  of  sediment  carried 
daily  into  the  Gulf  of  Mexico  by  the  Mississippi  River  is  equal  to  dumping 
mud  and  sand  into  the  waters  of  the  gulf  at  the  rate  of  over  thirty  car  loads 
of  twenty-five  tons  each  every  minute  continuously  day  and  night. 


io6  GENERAL  SCIENCE 

In  Physical  Geography  the  relation  of  erosion  to  valley 
formation  is  discussed  at  length,  together  with  the  wonder- 
ful results  accomplished  by  streams  in  making  broad  and 
deep  ways  for  themselves.  When  one  looks  upon  channels 
that  have  been  worn  down  through  solid  rock  hundreds  of 


FIG.  38. — The  Roosevelt  Dam  on  Salt  River,  Arizona,  is  280  feet  high.  It 
has  a  storage  capacity  sufficient  to  cover  with  water  1,367,000  acres  one  foot 
deep.  Below  the  dam,  and  out  of  sight  in  the  picture,  is  a  power-house 
capable  of  developing  7,500  horsepower. 


feet  in  depth,  and  miles  in  length,  the  power  of  running  water 
to  do  work  almost  passes  belief.  And  the  wonder  does  not 
grow  less  as  one  considers  that  this  continuous  flow  of  the 
waters  toward  sea-level  is  made  possible  by  their  continuous 
return  as  atmospheric  moisture  to  elevated  regions.  As 
result  of  solar  heating  and  the  vaporization  of  oceanic  waters 
and  the  precipitation  of  this  moisture  inland  on  the  higher 
levels,  the  flow  of  streams  is  continuous,  and  the  work  of 

-  .  A . 


WATER,  AND  ITS  USES 


107 


leveling  down  continents  goes  on  ceaselessly.  Wherever  the 
bedrock  of  the  earth's  crust  appears  at  the  surface  without 
any  covering  of  soil,  it  may  be  supposed  that  erosion  by  the 
agencies  of  wind  and  water  has  occurred,  and  that  the  dis- 
integrated rock  particles  resulting  from  weathering  have 
been  carried  elsewhere. 


Sr^sirKw^W 


FIG.  39. — Principal  irrigation  projects  in  western  United  States. 

SUMMARY 

The  navigable  streams  of  the  United  States  figure  largely  in  the 
history  of  its  exploration  and  settlement. 

Water  power  is  a  resource  fundamental  to  the  nation's  industrial 
life.  Agricultural  enterprise  on  the  largest  scale  is  possible  only  in 
broad  and  fertile  valleys  where  the  slopes  are  gentle,  and  the  soil  is  deep. 


io8 


GENERAL  SCIENCE 


Continued  erosion  of  hillsides  and  valley  slopes  is  a  menace  to  the 
wealth  of  the  nation.  There  is  need  for  intelligent  cultivation  of  the 
soil  on  the  steeper  slopes  to  conserve  its  productiveness. 

Irrigation  has  brought  under  cultivation  large  tracts  of  land  highly 
productive  when  well  watered.  Many  of  these  irrigation  projects  are 
government  enterprises  not  only  in  this  country  but  in  Egypt,  India, 
and  elsewhere. 

Hills  very  generally  represent  relatively  hard  formations  of  the 
earth's  crust  which  have  resisted  erosion.  In  general,  too,  the  slopes  of 
the  older  valleys  are  less  abrupt,  and  the  streams  through  them  are 
wider,  more  shallow,  and  slower  in  current. 


FIG.  40. — A  type  of  dredge  used  in  removing  sand  bars  and  silt  deposits  in 
the  Mississippi  River. 

A  "divide"  is  the  crest  at  the  upper  edge  where  two  slopes  meet, 
and  where  the  waters  from  rainfall  and  snowfall  drain  off  in  different 
directions.  A  river  system  consists  of  a  main  stream  and  all  its  tribu- 
taries. A  river  basin  is  the  land  area  whose  run-off  contributes  water 
to  a  river  system. 

Exercises 

1.  Name  sections  of  this  country  where  water  power  is  abundant  and  cheap. 
Why  is  it  not  so  in  other  well-watered  regions? 


WATER,  AND  ITS  USES  109 

2.  In  what  respects  is  electric  power  preferable  to  water  power?     What  rela- 
tion has  the  existence  of  water  power  to  cheap  and  abundant  electric 
power?     Mention  notable  illustrations  of  this  in  the  United  States. 

3.  What  advantages  are  there  in  transportation  by  inland  water  ways  over 
transportation  by  railroads?     What  limitations  are  there  for  the  former? 

4.  What  notable  illustrations  recorded  in  history  of  the  rise  of  nations  as  they 
have  engaged  in  foreign  commerce? 

5.  Name  ways  in  which  water  is  changing  the  surface  forms  of  earth  (a) 
under  man's  direction;  (6)  without  any  part  taken  by  man. 

6.  Tell  of  efforts  by  man  to  control  the  destructive  effects  of  surface  waters. 

7.  Explain  valley  formation  through  the  agency  of  water. 

8.  Why  is  running  water  more  likely  to  be  pure  than  stagnant  water? 


V.  THE  ATMOSPHERE 


PROPERTIES  AND  USES   OF  AIR 

We  are  accustomed  to  think  of  fish  and  other  marine  life 
as  living  in  the  waters  of  the  ocean.  But  we  are  less  likely 
to  speak  of  an  atmospheric  ocean  in  the  bottom  of  which 
birds  and  human  beings  live  and  move.  It  is  calculated 


'eiffhti 
i  miles 

35- 

Barometer 
heights  in 
inches 

"Tooo 

Air 
densith 

i 

30000 

75  - 

,./ 

I 

10-- 

% 

^ 

* 

6.. 

y^MffhuKsr 

»» 

*' 

J-- 

0  — 

^I^C^^-^^ 

--/5 

-JO 

f 

/ 

FlG.  41. — Depth  and  density  of  the  atmosphere.      (Tower,  Smith  &  Turton.) 

that  one-half  of  the  atmosphere  is  within  four  miles  of  the 
earth's  surface,  and  twenty-nine  thirtieths  of  it  within  fifteen 
miles  of  sea-level.  While  probably  all  of  it  is  inside  two 
hundred  miles  of  the  surface,  there  is  no  means  of  knowing 
positively  how  far  upward  it  may  extend.  The  highest 
altitude  reached  by  man  is  about  seven  miles.  By  reason  of 

no 


THE  ATMOSPHERE  III 

their  molecular  activities  the  gases  composing  the  atmosphere 
expand  outward  away  from  the  surface  until  the  earth's 
attraction  overcomes  their  expansive  power.  This  prevents 
complete  loss  of  these  air  particles  into  the  vast  spaces 
surrounding  the  earth. 

By  reason  of  the  readiness  with  which  air  is  compressed, 
the  lowermost  layers  in  which  man  lives  are  the  most  dense. 
As  a  person  ascends  a  mountain  or  goes  up  in  a  balloon,  there 
is  less  and  less  of  air  (and  of  oxygen)  in  any  one  breath  even 
when  the  lungs  are  filled  to  their  utmost  capacity.  As  the 
air  grows  more  and  more  rarefied,  in  order  to  provide  the 
needed  supply  of  oxygen  the  breathing  is  quickened  and 
becomes  labored.  In  time  distress  is  experienced,  and  a  person 
may  become  unconscious.  In  balloon  ascensions  resort  is 
sometimes  made  to  artificial  respiration,  pure  oxygen  gas  com- 
pressed into  tanks  being  taken  along  and  breathed  as  needed. 

The  notions  of  the  ancients  concerning  the  natural  agencies 
against  which  man  has  to  contend,  and  whose  nature  was  but 
dimly  comprehended  if  at  all,  is  illustrated  in  the  myth  of 
Aeolus1  and  his  bag  of  winds.  Disregarding  any  moral  that 
may  be  implied,  there  is  no  suggestion  in  it  of  any  con- 
ception of  whence  winds  come  and  whither  they  go.  Litera- 
ture is  filled  with  references  to  the  winds.  Poetry  and  song 
abound  in  allusions  to  them  in  terms  more  or  less  true  to 
nature.  It  would  be  a  great  pity  if,  in  coming  to  know 
better  the  causes  of  natural  phenomena,  this  age  of  scientific 
thought  and  achievement  should  lose  any  part  of  the  rich 
inheritance  of  poetic  fancy,  though  at  times  it  does  take 
strange  liberties  with  scientific  fact.  References  of  this 
character  range  from  the  loftiest  heights  of  prophetic  vision2 
to  the  simple  rhymes  of  the  nursery3. 

1  See  story  of  homeward  journey  of  Ulysses  and  his  companions. 

2  See  Psalms  147,  148. 

3  See  "T.he  Wind"  by  Robert  Louis  Stevenson. 


112  GENERAL  SCIENCE 

The  atmosphere  is  washed  free  of  various  gases  and  of 
suspended  solid  matter  by  the  rains,  and  kept  constantly 
agitated  and  uniformly  mixed  by  diffusion  and  by  air  cur- 
rents. Sunlight  kills  many  bacteria  floating  in  it,  and  oxida- 
tion disposes  of  much  matter  in  the  air  of  plant  and  animal 
origin.  Growing  plants  in  sunlight  are  all  the  time  with- 
drawing carbon  dioxide  from  the  air  and  returning  ap- 
proximately the  same  volume  of  oxygen  gas  to  it.  Air  has 
weight  just  as  does  all  other  matter  whether  solid,  liquid,  or 
gaseous.  Although  this  weight  varies  under  different  con- 
ditions of  temperature  and  pressure,  it  is  approximately  one 
and  one-fourth  ounces  per  cubic  foot. 

The  lower  layers  of  the  atmosphere  at  all  times  contain 
more  or  less  of  water  particles  as  clouds,  and  water  in  the 
form  of  vapor,  and  varying  quantities  of  dust  and  smoke 
particles.  Of  the  heat  received  from  the  sun  it  is  calculated 
that  60  per  cent  does  not  get  through  to  the  earth's  surface, 
being  arrested  in  the  atmosphere.  However,  that  which 
does  get  through  to  the  land  and  water  surfaces  is  hindered 
even  more  by  this  same  blanket  of  the  lower  atmosphere 
from  escaping  into  space  by  radiation.  A  frost  is  much  less 
likely  when  the  sky  is  beclouded,  or  the  air  is  filled  with 
smoke. 

About  78  per  cent  of  the  air  is  nitrogen  gas.  This  nitrogen 
is  of  course  breathed  in  and  out  of  the  lungs  along  with  the 
oxygen.  It  is  non-poisonous  and  harmless,  and  it  does  not 
support  life.  It  is  characterized  by  its  negative  qualities, 
and  is  tasteless,  colorless,  odorless,  and  chemically  inert 
(inactive).  It  so  dilutes  the  oxygen  of  the  air  that  the 
oxidation  in  the  body  is  kept  within  bounds.  If  the  air  con- 
tained a  larger  per  cent  of  oxygen,  fires  once  started  might 
easily  become  uncontrollable. 

Compounds  of  nitrogen  in  the  soil  in  soluble  form  are 
indispensable  in  plant  growth,  and  in  this  way  contribute 


THE  ATMOSPHERE  113 

directly  to  man's  supply  of  foodstuffs.  The  supply  of 
nitrogen  in  the  atmosphere  is  inexhaustible.  None  of  man's 
efforts,  however,  to  form  food  materials  for  plants  direct 
from  atmospheric  nitrogen  in  large  quantities  and  at  rela- 
tively low  cost  have  been  successful  to  the  extent  desired. 
To  maintain  and  to  increase  the  content  of  the  soil  in  its 
nitrogen  compounds  suitable  for  plant  growth  is  a  problem 
of  science  directly  concerned  with  the  feeding  of  the  world's 
population. 

SUMMARY 

The  atmosphere  as  a  mixture  of  gases  has  the  properties  common  to 
all  matter  in  a  gaseous  form.  Its  composition  is  approximately  78  per 
cent  nitrogen,  about  21  per  cent  oxygen,  i  per  cent  argon,  and  21  oo 
per  cent  carbon  dioxide.  Water  vapor  and  dust  are  present  in  varying 
proportions. 

It  is  believed  that  the  atmosphere  may  extend  outward  from  the 
earth's  surface  two  hundred  miles  more  or  less,  but  by  reason  of  its 
compressibility  one-half  of  it  is  within  four  miles  of  sea-level,  and 
twenty-nine  thirtieths  of  it  within  fifteen  miles  of  the  earth's  surface. 
These  calculations  are  based  upon  readings  of  barometers  that  have 
been  carried  upward  to  different  altitudes,  and  upon  calculations  of 
the  height  of  meteors  when  first  seen. 

So  completely  is  the  atmosphere  mixed  by  its  own  diffusion  and  by 
winds  that,  aside  from  its  content  of  water  and  dust,  very  little  varia- 
tion in  its  composition  is  found  at  different  places  and  at  different 
times.  The  withdrawal  of  oxygen  from  the  air  by  animals,  and  the 
increase  in  its  per  cent  of  carbon  dioxide  due  to  respiration  and  com- 
bustion, is  counterbalanced  by  the  action  of  plants  in  abstracting 
carbon  dioxide  from  the  air  and  setting  oxygen  free. 

Winds  are  named  according  to  the  directions  from  which  they  blow. 
It  is  likely  that  the  directions  of  ocean  currents  in  some  cases  is  largely 
shaped  by  the  direction  of  prevailing  winds. 

Atmospheric  conditions  directly  affect  health.  A  cold  damp  air 
chills  the  body  surface  causing,  it  may  be,  colds  and  other  more  serious 
ailments.  Very  dry  air  is  injurious  to  the  mucous  lining  of  the  air- 
passages,  and  by  its  irritating  effects  may  upset  the  nervous  equilibrium 
of  the  body.  The  air-passages  and  lungs  are  not  only  irritated  by  dust 
blown  about,  but  disease  germs  become  widely  scattered  by  the  air. 


114  GENERAL  SCIENCE 

PRESSURE  EXERTED  BY  THE  ATMOSPHERE,  AND  EFFECT  OF 
PRESSURE  ON  GASES 

When  masses  of  air  have  a  velocity  of  many  miles  an  hour 
as  winds  we  have  evidence  of  the  great  pressure  exerted  by 
the  air.  We  can  feel  it  push  against  us  as  we  are  hurried 
along  by  it  in  its  course,  or  as  we  struggle  against  it  when 
breasting  a  gale.  It  is  calculated  that  when  a  wind  is 
blowing  at  the  rate  of  twenty  miles  an  hour  its  pressure  upon 
any  surface,  such  as  the  side  of  a  building,  is  approximately 
two  pounds  per  square  foot.  At  sixty  miles  per  hour  this 
pressure  becomes  eighteen  pounds,  and  at  one  hundred 
miles  per  hour  fifty  pounds  per  square  foot.  The  pressure 
increases  as  the  square  of  the  increase  in  velocity.  Winds 
approaching  this  greatest  velocity  are  known  as  hurricanes, 
and  their  destructive  violence  can  readily  be  understood. 

When  the  atmosphere  is  calm,  however,  we  do  not  ordi- 
narily appreciate  the  fact  that  it  exerts  any  pressure  upon 
exposed  surfaces.  This  pressure  may  be  thought  of  as  the 
weight  of  a  column  of  air  reaching  downward  from  the  upper- 
most level  of  the  atmosphere,  and  having  a  cross-section  the 
same  as  that  of  the  body  pressed  upon.  The  weight  of  the 
mercury  contained  in  a  barometer  tube  is  used  to  measure 
the  value  of  atmospheric  pressure.  At  sea-level  the  height  of 
the  mercury  column  averages  about  thirty  inches  (or  76  cm.), 
and  this  height  is  taken  as  the  standard  for  atmospheric 
pressure.  As  the  weight  of  a  column  of  mercury  thirty 
inches  high  and  one  square  inch  cross-section  is  about  fourteen 
and  one-half  pounds,  the  pressure  of  the  atmosphere  at  sea- 
level  must  be  fourteen  and  one-half  pounds  per  square  inch. 
This  amount  of  pressure  by  any  gas  is  often  spoken  of  as 
"one  atmosphere."  In  making  barometers  great  care  is 
exercised  that  the  space  above  the  mercury  in  the  tube  shall 
be  free  of  air. 


THE  ATMOSPHERE  115 

Air  penetrating  the  tissues  of  our  bodies  maintains  a  pres- 
sure within  equal  and  opposite  to  the  pressure  from  without. 
We  are  unconscious  of  the  existence  of  any  such  air  pressure 
until  in  some  way  an  inequality  is  brought  about  in  it. 

For  changes  in  altitude  on  or  near  the  earth's  surface  the 
barometer  falls  about  one  inch  for  every  1000  feet  elevation. 
In  balloon  ascensions  where  the  rise  is  rapid,  the  aeronaut 


PIG.  42. — The  manufacture  of  artificial  ice.  V,  Valve  regulating  pressure; 
A,  water  supply,  and  drip,  to  carry  off  heat  from  compression  of  the  ammonia 
gas;  /,  containers  of  distilled  water  to  be  frozen;  S,  brine  (solution  of  low 
freezing  temperature);  B,  compression  chamber;  C,  expansion  chamber. 

sometimes  bleeds  at  the  nose  and  mouth  because  of  the 
rupture  of  the  walls  of  blood  vessels.  This  is  due  to  the  fact 
that  the  gaseous  pressure  within  the  blood  soon  becomes 
greater  than  the  outer  air  pressure,  the  latter  being  rapidly 
reduced  because  of  the  ascent. 

It  is  customary  not  to  fill  balloons  full  of  gas  before  they 
are  sent  up  owing  to  the  expansion  of  the  gas  as  the  balloon 
rises  into  the  less  dense  upper  atmosphere.  The  heat  of  the 


n6 


GENERAL  SCIENCE 


GLASS  NECK 


METAL  NECK 


RUBBER 


direct  rays  of  the  sun  may  intensify  this  increase  in  volume, 
and  there  is  great  risk  of  bursting  the  gas  envelope. 

By  compressing  gases  sufficiently 
it  is  possible  to  cause  a  change  in 
them  from  the  gaseous  to  a  liquid 
state.  When  this  pressure  is  re- 
leased the  liquid  changes  back  to 
the  gaseous  form.  In  the  change 
from  a  liquid  to  a  gas  a  large 
amount  of  heat  disappears  (be- 
comes "  la  tent").  It  is  used  in 
giving  increased  velocity  to  the 
molecules  of  the  gas.  A  common 
application  of  this  fact  is  in  the 
manufacture  of  artificial  ice1.  An 
exhaust  pump  is  employed  to  con- 
tinuously remove  ammonia  gas 
from  pipes  containing  liquid  am- 
monia so  that  vaporization  goes 
on  in  them  rapidly.  This  same 
pump  may  also  serve  as  a  com- 
pressor to  force  the  ammonia  gas 
much  compressed  (perhaps  lique- 
fied) back  into  the  pipes  of  the 
cooling  tank.  The  same  ammonia 
PIG.  43.— A  thermos  bottle,  is  thus  used  repeatedly  to  cool 

The  air  was  withdrawn  from  the  sajt  solution  (see  page  99)  in 
between  the  double  glass  walls, 

and  the  opening  then  sealed  which  the  pipes  are  submerged. 
&£?&£L%&3  The  energy  required  to  run  the 
the  bottle.  The  metal  case  is  pump  and  compressor  is  furnished 

for   protection    only.       (Tower, 

Smith  &•  Turton.)   '  by  an  engine. 

1  A  discussion  of  the  steps  involved  usually  may  be  found  in  texts  in 
Physics  in  connection  with  the  subject  of  heat,  and  in  Chemistry  in  connection 
with  the  topic  ammonia. 


THE  ATMOSPHERE  117 

With  powerful  pumps  it  is  possible  to  so  compress  air  in 
pipes  capable  of  withstanding  great  strain  that  when  the 
compressed  air  is  cooled  to  a  very  low  temperature  it  changes 
to  a  liquid  state,  and  becomes  liquid  air.  It  then  looks  very 
much  like  water.  As  the  air  is  being  compressed  its  tempera- 
ture is  raised  by  reason  of  the  crowding  together  of  its  mole- 
cules. The  pipes  containing  it  can  be  kept  cool,  however, 
by  allowing  water  to  run  over  them  to  carry  away  the 
aheat  of  compression."  When  stop  cocks  in  the  pipes  are 
now  opened  a  very  little,  allowing  an  outrush  of  some  of  the 
highly  compressed  air  into  an  enclosed  space  around  the 
pipes,  its  expansion  is  so  excessive  that  its  temperature  and 
that  of  the  compressed  air  within  the  pipes  is  greatly  lowered. 
While  there  is  loss  of  much  of  the  compressed  air  in  its  return 
to  its  normal  density,  other  portions  of  it  will  be  changed  to  a 
liquid  form  by  reason  of  the  low  temperature.  Liquid  air 
must  be  kept  in  containers  that  are  like  " thermos"  bottles 
in  having  double  walls  from  between  which  the  air  has  been 
withdrawn.  These  containers  must  not  be  kept  stoppered 
other  than  with  a  plug  of  cotton  since  the  enormous  expan- 
sion in  volume  of  this  air  as  it  slowly  changes  back  to  the 
gaseous  form  would  cause  destructive  explosions. 

Among  the  many  things  that  are  fascinating  in  the  story 
of  liquid  air,  mention  can  be  made  here  only  of  its  use  as  a 
source  of  nearly  pure  oxygen  gas  at  a  relatively  low  cost  of 
production.  The  atmosphere  is  largely  composed  of  oxygen 
and  nitrogen  gases  in  the  proportion  of  about  four  volumes 
of  nitrogen  to  one  of  oxygen.  When  air  is  liquefied  it  con- 
sists of  a  mixture  of  liquid  oxygen  and  liquid  nitrogen.  Any 
water  vapor  and  any  carbon  dioxide  gas  present  in  the  air 
at  first  will  have  been  eliminated  by  having  been  solidified 
(frozen).  At  ordinary  temperatures  and  pressures  this 
liquefied  air  changes  back  to  the  gaseous  condition  rapidly, 
and  in  this  vaporization  the  liquid  nitrogen  changes  to  a  gas 


n8  GENERAL  SCIENCE 

first  leaving  an  almost  pure  liquid  oxygen.  This  oxygen  as 
a  much  compressed  gas  in  strong  steel  cylinders  can  be  trans- 
ported for  use  anywhere. 

SUMMARY 

Differences  in  atmospheric  pressure  are  due  to  differences  in  density. 
This  change  in  density  results  from  changes  in  temperature  and  from 
variations  in  the  amount  of  water  vapor  present  in  the  air.  The  higher 
the  temperature  and  the  greater  the  amount  of  water  vapor  the  less 
the  density. 

The  rise  and  fall  of  the  mercury  column  in  the  barometer  measures 
the  varying  pressure  of  the  atmosphere  whatever  the  occasion  of  its 
change  in  density.  Any  considerable  fall  of  the  barometer  within  a 
short  time  usually  indicates  a  marked  increase  in  the  amount  of  water 
vapor  in  the  atmosphere,  making  more  probable  the  precipitation  of 
some  of  it  as  rain  or  snow. 

The  volume  of  any  gas  is  inversely  proportional  to  the  pressure  upon 
it. 

Gases  may  be  changed  to  liquids  by  subjecting  them  to  high  pressure 
and  low  temperature.  The  heat  resulting  from  their  compression  is 
easily  disposed  of  by  allowing  cold  water  to  flow  over  the  pipes  in 
which  the  gas  is  confined. 

Compressed  gases  when  allowed  to  expand  abstract  from  surrounding 
bodies  an  amount  of  heat  equal  to  what  was  freed  in  compressing  them. 
The  cooling  effect  of  compressed  gases  when  allowed  to  expand  is  ex- 
tensively used  in  maintaining  low  temperatures  in  cold  storage  houses, 
in  the  manufacture  of  artificial  ice,  and  in  keeping  large  buildings  cool 
in  summer. 

Ammonia  gas  is  a  by-product  of  the  plants  where  illuminating  gas 
is  made.  This  gas  is  easily  liquefied,  and  it  can  be  purchased  in  the 
liquid  form  confined  in  heavy  steel  cylinders.  It  is  to  be  remembered 
that  the  ammonia  water  of  the  laboratory  and  the  laundry  is  merely 
water  containing  ammonia  gas  in  solution. 

The  temperatures  at  which  different  gases  change  to  liquids  when 
under  the  same  pressure  vary  widely.  For  the  same  gas  it  is  always 
the  same. 

APPLICATIONS  OF  ATMOSPHERIC  PRESSURE 
That  man  can  live  and  move  about  far  below  the  surface 
of  water,  that  he  can  build  foundations  for  bridges  out  in 


THE  ATMOSPHERE 


mid-stream  from  bedrock  upward,  and  that  he  can  carry 
on  warfare  beneath  the 
waves  of  the  ocean,  seems 
marvelous.  These  achieve- 
ments rank  with  man's 
mastery  of  the  atmosphere 
in  which  he  makes  the  air 
a  highway  for  travel  and 
for  sport,  and  a  place  for 
carrying  on  warfare.  But 
at  all  times  and  everywhere 
man  must  be  provided 
with  an  abundance  of  air 
to  breathe,  or  death  from 
lack  of  oxygen  speedily 
follows. 

By  use  of  powerful  com- 
pression pumps  large  vol- 
umes of  air  may  be  made 
to  occupy  little  space 
within  a  submarine.  By 
its  withdrawal  from  one 
side  of  an  air- tight  movable 
partition  water  can  push 
its  way  into  the  boat, 
causing  it  to  sink.  By 
allowing  the  compressed 
air  to  expand  this  water 
is  again  driven  out,  and 
the  boat  is  so  lightened 
that  it  will  come  to  the 
surface.  By  use  of  electric 
motors,  the  boat  is  rapidly 
propelled  through  the  water  beneath  the  surface,  and  its 


120  GENERAL  SCIENCE 

rise  to  surface  or  its  descent  into  the  depths  greatly 
accelerated.  Small  but  powerful  gas  engines  are  used  when 
the  submarine  is  at  the  surface.  Electricity  from  dynamos 
and  storage  batteries  furnishes  light  for  the  boat. 

While  provision  can  be  made  to  keep  up  artificial  respira- 
tion for  a  considerable  length  of  time,  any  accident  to  the 
machinery  of  a  submarine  when  submerged  is  likely  to  result 
in  its  becoming  the  burial  casket  for  its  imprisoned  crew. 
So  enormous  is  the  pressure  of  the  water  outside  at  any 
considerable  depth1  that  attempts  to  escape  through  any 
opening  made  in  the  side  of  the  craft  may  be  futile. 

Caissons  (ka'-sonz)  are  usually  large  hollow  steel  cylinders 
made  up  of  short  lengths  riveted  together.  These  sections 
when  taken  to  the  place  where  a  bridge  pier  is  to  be  built  are 
lowered  into  the  water  one  at  a  time,  and  on  top  of  one 
another,  till  the  lowermost  one  reaches  bottom.  Each 
section  in  turn  is  riveted  to  the  upper  edge  of  the  section 
last  lowered  into  the  water.  While  this  is  being  done  the 
cylinder  hangs  suspended.  It  is  weighted  by  masonry 
built  within  it  to  keep  it  down  in  the  water,  and  to  prevent 
its  being  swept  away.  The  lowermost  part  of  the  cylinder 
is  an  air-tight  chamber,  and  compressed  air  forced  into  this 
chamber  from  above  keeps  out  the  water.  Excavation  can 
then  go  on  inside  the  bottom  of  the  cylinder,  allowing  it  to 
settle  deeper  and  deeper  by  reason  of  its  own  weight.  The 
material  excavated  is  hoisted  out  through  shafts  having 
" air-locks"  (partitions)  that  prevent  escape  of  the  com- 
pressed air.  In  due  time  from  the  bedrock  up  the  cylinder 
is  filled  with  solid  masonry. 

When  workmen  pass  into  or  out  of  the  working  chambers 

1  The  pressure  of  water  in  pounds  per  square  foot  upon  a  submerged  body 
is  found  by  multiplying  62.4  pounds  (the  weight  of  one  cubic  foot  of  water) 
by  the  depth  of  the  body  below  surface.  In  sea  water  the  weight  per  cubic 
foot  is  about  2^  per  cent  greater. 


THE  ATMOSPHERE 


121 


FIG.  45. — Caissons.  A ,  the  working  chamber  where  excavation  goes  on  in 
an  atmosphere  of  such  density  (and  pressure)  that  water  from  without  is  kept 
from  entering;  B,  air-tight  shaft  through  which  workmen  and  material 
pass  up  and  down;  E,  E',  chambers  through  which  workmen  pass  to  and  fro 
from  the  cage,  and  where  the  atmospheric  pressure  to  which  they  are  sub- 
jected is  gradually  changed.  F,  Fr,  ballast  of  masonry  to  keep  caisson  in 
place;  G,  pipe  conveying^air  under  great  pressure  into  the  caisson  chambers. 


122  GENERAL  SCIENCE 

where  the  air  pressure  is  being  maintained,  it  is  necessary 
that  the  change  in  air  density  affecting  their  bodies  be  made 
gradually.  This  is  done  in  order  to  permit  an  equalization 
of  density  of  air  within  the  body  and  without.  Serious 
results  follow  if  sufficient  time  is  not  taken  to  provide  for 
this. 

SUMMARY 

The  great  pressure  exerted  by  compressed  air  makes  it  an  effective 
agent  for  doing  work.  Its  escape  from  pipes  and  hose,  by  means  of 
which  it  can  be  taken  anywhere,  is  so  easily  controlled  that  its  uses 
are  manifold  and  of  great  economic  importance. 

Air-brakes  have  made  possible  a  large  increase  in  the  speed  of  railway 
trains,  and  a  decrease  in  danger  from  accidents,  by  reason  of  the  fact 
that  the  engineer  is  given  complete  control  of  a  train  through  their  use. 

Air  drills  have  revolutionized  mining,  tunnel  building,  and  all  engi- 
neering enterprises  involving  the  removal  of  rock  by  blasting.  By  aid 
of  compressed  air  excavations  can  be  made  beneath  water  when  not 
too  deep,  and  solid  masonry  put  in  place  under  water  from  the  bed- 
rock upward. 

Where  drilling  is  done  by  use  of  compressed  air  in  mines  and  in 
tunnel  headings,  the  escaping  air  serves  to  provide  the  necessary 
ventilation  for  the  workmen. 

Compressed  air  in  the  tires  of  bicycles  and  automobiles  makes  riding 
a  comfort.  Without  spraying  outfits  employing  compressed  air  the 
fruit  grower  could  not  wage  profitable  warfare  upon  insect  enemies 
and  fungus  growths.  Submarine  navigation  involves  the  use  of  com- 
pressed air  in  controlling  submergence  of  the  boats,  and  for  air  supply 
to  the  persons  aboard  the  boats. 

Water  pumps  commonly  employ  the  pressure  of  the  atmosphere  to 
raise  water  above  a  valve  placed  some  thirty  feet  more  or  less  above 
the  water  surface.  This  height  varies  with  the  density  of  the  atmos- 
phere, and  its  consequent  pressure.  The  flow  of  water  through  siphons 
where  it  runs  "up-hill"  part  of  the  way  is  due  to  atmospheric  pressure. 

Exercises 

Get  information  from  all  sources  at  hand  upon  some  or  all  of  the  topics 
named  below.  Describe  the  construction  and  operation  of  these  appliances. 
Use  drawings  wherever  helpful  to  clearness.  Be  concise  in  the  descriptions. 


THE  ATMOSPHERE  123 

1.  Air  drills,  and  their  uses  in  mines  and  tunnel  building.     Their  advantages 
over  the  old  hand  drills  (a)  in  amount  of  work  accomplished;  (b)  in  the 
health  of  the  workmen. 

2.  Pneumatic  tubes,  and  their  uses  as  change  carriers  in  stores. 

3.  Vacuum   cleaners,    and    their   uses    for   household    purposes.     The    care 
necessarily  given  them,  and  the  causes  of  their  failure  to  give  satisfactory 
service  at  times. 

4.  Air-brakes,  and  their  uses  on  railway  trains. 

6.  The  construction  and  operation  of  an  artificial  ice  plant.  Make  use  of 
a  diagram,  and  be  sure  to  make  very  clear  the  part  played  in  the  process 
by  heat  of  vaporization. 

6.  The  sand  blast,  and  the  uses  to  which  it  is  put. 

7.  Spraying  outfits  used  by  fruit  growers,  and  for  painting  large  structures, 
or  surfaces  where  hand  work  is  too  difficult  or  too  expensive. 

8.  Pneumatic  hammers  used  in  riveting  together  the  steel  frames  of  bridges, 
large  buildings,  and  other  structural  work. 


CURRENTS  IN  THE  ATMOSPHERE,  AND  THEIR  RELATION  TO 
ATMOSPHERIC  PRESSURE 

It  is  not  infrequently  noted  that  when  a  great  fire  occurs  a 
wind  begins  blowing,  fanning  the  flames  and  driving  on  the 
fire.  The  great  masses  of  air  heated  by  the  fire  have  a 
lessened  density  as  result  of  expansion  due  to  the  heat,  and 
a  pressure  less  than  that  of  the  surrounding  air.  The  result 
of  this  is  an  inrush  of  the  denser  air  from  all  sides,  and  the 
warmed  air  is  crowded  upward  as  the  direction  of  least 
resistance.  The  usual  statement  concerning  this  condition 
is  that  when  the  air  is  warmed  it  rises,  and  the  cooler  air 
rushes  in  to  take  its  place.  This  mistakes  cause  and  effect. 
The  less  its  density  the  greater  the  ease  with  which  the  air 
is  crowded  upward,  and  the  more  rapid  its  ascent. 

The  presence  of  water  vapor  in  the  atmosphere  lessens  its 
density.  If  water  vapor  is  added  to  any  certain  amount 
of  dry  air,  the  combined  weight  must  of  course  be  greater 
than  the  weight  of  the  air  alone.  But  moisture-laden  air 
weighs  less  per  cubic  foot  than  dry  air.  If  now  from  the 
weight  of  a  cubic  foot  of  saturated  air  is  taken  the  weight  of 


124 


GENERAL  SCIENCE 


the  water  in  it,  the  weight  of  the  dried  air  remaining  is 
found  to  be  less  than  what  the  weight  of  a  cubic  foot  of  dry 
air  at  that  temperature  should  be.  Evidently  the  decrease 
in  density  of  air  to  which  water  vapor  is  added  results  from 
the  replacement  of  some  air  by  water  vapor  whose  density 
is  only  about  five-eighths  (.62)  as  great  as  that  of  dry  air. 
In  its  change  from  the  liquid  to  the  gaseous  state  water 
increases  in  volume  about  sixteen  hundred  fold. 


FIG.  46. — In  changing  from  a  liquid  to  a  vapor  water  expands  about  sixteen 
hundred  fold.     (Tower,  Smith  &  Turton.) 

As  a  rule  the  winds  that  spring  up  at  times  of  great 
conflagrations  blow  in  one  direction  only,  becoming  often- 
times a  gale  in  violence.  To  account  for  this  it  may  be 
supposed  that  the  atmospheric  pressure  is  greater  at  a 
place  in  some  one  direction  from  the  ascending  warmed  air, 
and  that  the  inrush  from  that  side  is  more  marked. 
Gradually  the  air  current  or  wind  from  that  direction 
becomes  dominant,  supplying  the  volume  of  air  of  the  as- 
cending current  so  completely  that  any  movement  of  air 
inward  from  other  directions  is  not  noticeable. 

This  condition  of  atmospheric  movement  as  a  result  of 


THE  ATMOSPHERE  125 

the  fire  may  be  likened  to  a  high  chimney  or  smoke  stack 
through  which  is  maintained  a  violent  uprush  or  draft 
hundreds  of  feet  in  height.  This  will  be  continued  as  long 
as  sufficient  heat  is  supplied  from  the  fire  below.  In  some 
respects  this  condition  resembles  that  existing  in  and  about 
the  funnel  of  a  tornado  whose  passage  across  a  country 
leaves  a  trail  of  destruction.  Fortunately  the  width  of  the 


FIG.  47. — The  tornado  is  a  storehouse  of  energy. 

track  of  the  tornado  is  often  scarcely  more  than  fifty  or  one 
hundred  feet  and  rarely  more  than  one-half  mile.  While 
the  velocity  of  the  air  whirl  about  the  funnel  may  at  times 
approach  two  hundred  miles  or  more  an  hour,  the  progress 
across  country  may  be  only  forty  or  fifty  miles  per  hour. 

In  the  case  of  the  tornado  the  heat  required  to  maintain 
the  updraft  is  largely  the  latent  heat  (heat  of  vaporization) 
which  is  set  free  as  a  result  of  the  condensation  of  atmos- 
pheric moisture.  (See  page  96.)  When  moisture-laden 
air  feeds  into  the  upward  moving  air  current,  it  expands 
very  rapidly,  with  an  accompanying  fall  in  temperature  and 


126  GENERAL  SCIENCE 

the  condensation  of  much  moisture.  It  is  to  this  excessive 
condensation  and  consequent  heavy  rainfall  that  the  inky 
black  cloud  accompanying  the  tornado  is  usually  due.  At 
times  more  or  less  of  dust  and  soil  is  carried  up  by  the  rising 
air  currents.  The  more  moisture  there  may  be  in  the  air 
the  more  of  condensation  there  will  be.  The  more  latent 
heat  there  is  liberated  the  greater  will  be  the  upward  rush 
within  the  funnel  of  the  tornado.  As  the  supply  of  moisture- 
laden  air  lessens,  the  violence  of  the  storm  subsides,  and  the 
tornado  may  thus  die  out  because  of  lack  of  heat  energy. 

The  air  that  constitutes  a  tornado  has  a  violent  whirling 
motion.  As  a  result  of  this  the  interior  of  the  whirl  is 
likely  to  be  very  much  rarefied,  approaching  more  or  less 
the  condition  in  a  vacuum.  As  the  warmed  air  rises,  its 
ascent  becomes  a  spiral,  and  in  the  northern  hemisphere 
the  direction  of  the  whirl  is  to  the  right  around  the  centre  of 
motion.  In  dusty  roadways  on  hot  days  in  summer  there 
are  often  seen  illustrations  of  this  air  movement  in  the  dust 
whirls  that  spring  up  apparently  without  any  disturbance 
whatever  from  passing  air  currents.  In  such  cases  the 
highly  heated  air  would  seem  to  have  broken  its  way  through 
and  upward,  and  to  rise  with  sufficient  energy  to  carry  with 
it  in  its  whirling  motion  some  of  the  finer  dust  particles. 

SUMMARY 

Wind  is  a  term  that  very  properly  may  be  restricted  to  air  currents 
along  the  earth's  surface  of  sufficient  velocity  to  be  noticeable.  Winds 
are  the  direct  result  of  inequality  of  pressure  in  different  parts  of  the 
atmosphere,  the  result  of  unequal  heating  and  of  varying  amounts  of 
moisture. 

All  air  currents,  including  winds,  may  be  considered  as  efforts  to 
restore  equilibrium  in  an  atmospheric  pressure  that  is  all  the  time  being 
disturbed  by  solar  heating,  and  by  the  processes  of  vaporization  and 
condensation. 

Somewhere  off  in  the  general  direction  toward  which  the  wind  is 
blowing  the  air  of  lighter  density  and  lesser  pressure  is  being  forced 


THE  ATMOSPHERE 


127 


upward  away  from  the  earth's  surface  as  an  ascending  air  current, 
thus  ceasing  to  be  a  wind.  And  somewhere  off  in  the  general  direction 
from  which  the  wind  comes  we  may  suppose  that  there  is  a  region 
where  cool,  dry,  and  therefore  dense  air  is  settling  down  from  the  upper 
atmosphere. 

In  tornadoes  not  only  is  there  an  uprush  of  air  having  great  velocity, 
but  at  the  same -time  this  ascending  air  may  have  a  far  swifter  whirling 
motion  that  causes  it  to  rise  with  a  spiral  movement,  and  to  have  a 
twisting  effect  on  objects. 


FIG.  48. — The  effects  of  a  tornado. 


The  central  portions  of  the  funnel  of  the  tornado  may  be  considered 
as  more  or  less  a  vacuum.  This  results  from  the  whirling  motion 
which  throws  the  air  outward  away  from  the  centre  of  the  rising  column. 

Buildings  more  or  less  tightly  closed,  and  caught  in  the  centre  of 
the  track  of  a  tornado,  are  sometimes  found  with  their  walls  pushed 
outward  by  the  air  which  was  confined  within  them.  The  air  outside 
them  must  have  been  almost  instantly  and  completely  withdrawn 
upward  and  away  from  them. 


128  GENERAL  SCIENCE 

AREAS  OF  HIGH  AND  Low  PRESSURE 

The  rotation  of  the  earth  is  one  of  the  great  factors  in 
establishing  the  direction  of  the  air  currents  of  the  earth  as 
a  whole.  At  the  equator  the  velocity  eastward  of  the  earth's 
surface  is  about  seventeen  miles  per  minute  (25,000  miles 
in  24  hours) .  The  atmosphere  resting  on  the  land  and  water 
surfaces  shares  in  this  eastward  velocity.  It  is  a  rate  much 
greater  than  the  drift  of  the  upper  air  currents  from  the 
equatorial  region  toward  the  poles. 

As  a  resultant  of  these  two  motions  (velocities)  northward 
and  eastward,  the  upper  air  currents  of  the  northern  hemi- 
sphere instead  of  following  a  meridian  due  northward  drift 
toward  the  northeast,  and  perhaps  somewhat  more  easterly 
than  northerly. 

By  reason  of  the  earth's  rotation,  too,  the  winds  (surface 
currents)  in  the  northern  hemisphere  blowing  toward  the 
equator  pass  over  regions  of  greater  and  greater  eastward 
velocity  as  they  approach  the  equator.  This  southward 
moving  air  does  not  acquire  this  eastward  motion  of  the 
earth's  surface  readily  enough  to  maintain  a  southerly 
direction  along  a  meridian,  but  is  all  the  time  being  left 
behind  (deflected)  to  the  westward.  Its  direction  across  the 
earth's  surface  instead  of  being  due  south  is  southwesterly, 
i.e.,  it  becomes  a  northeast  wind. 

As  the  causes  which  accomplish  these  results  are  con- 
tinuously operative,  the  trade  winds  of  the  northern  hemi- 
sphere as  well  as  like  winds  in  the  southern  hemisphere  are 
quite  constant  both  in  direction  and  in  velocity.  This 
movement  is  especially  marked  on  the  oceans  where  dis- 
turbing factors  do  not  enter  in  to  overcome  or  divert  them. 

In  the  middle  latitudes,  as  in  the  United  States,  this 
planetary  circulation  (air  currents  of  the  earth  as  a  whole) 
controls  wind  direction  only  in  part.  The  course  taken  by  the 


THE  ATMOSPHERE 


129 


wind  in  these  regions  is  almost  wholly  a  matter  of  the  direc- 
tion of  an  inrush  of  surface  air  into  areas  of  low  pressure,  or 
of  an  outrush  from  areas  of  high  pressure.  In  other  words 


FIG.  49. — The  direction  of  winds  into  a  low.  The  solid  lines  are  isobars, 
and  the  shaded  areas  in  the  east  and  southeast  quadrants  show  where  pre- 
cipitation commonly  occurs.  The  whole  storm  area  may  be  thought  of  as 
an  inverted  funnel  with  its  centre  of  least  pressure  the  place  for  escape  of.  air 
upward. 

this  is  a  region  of  variable  winds  controlled  almost  wholly 
by  the  successive  passages  across  country  of  areas  of  high 
and  low  pressure. 

The  conditions  that  have  been  discussed  above  cause  the 


130  GENERAL  SCIENCE 

flow  of  air  into  a  \owfrom  the  south  to  be  deflected  toward  the 
right  (east) .  The  flow  into  a  low  from  the  north  is  likewise 
deflected  towards  the  right  (now  the  west).  As  the  inflow 
from  the  other  sides  of  the  low  are  affected  in  a  like  manner, 
the  winds  entering  the  area  of  low  pressure  from  all  sides 
suffer  deflection  to  the  right.  They  move  into  the  centre  of 
the  low  with  a  spiral  motion  whose  direction  in  the  northern 
hemisphere  is  opposite  that  of  the  hands  of  a  clock,  or 
counter-clockwise . 

Whether  the  velocity  of  the  parts  of  this  great  whirling 
mass  of  air  about  the  central  rising  column  is  great  or  small 
depends  upon  the  relative  densities  and  consequent  pressures 
of  adjacent  portions  of  the  atmosphere.  These  variations  in 
pressure  will  of  course  be  shown  in  the  readings  of  barome- 
ters in  different  localities. 

This  mass  of  disturbed  atmosphere  having  a  progressive 
motion  in  an  easterly  direction,  and  a  whirling  motion  about 
its  rising  air  current,  may  be  many  hundreds  of  miles  in 
diameter  while  possibly  but  a  few  hundreds  of  feet  in  vertical 
thickness.  It  is  the  cyclone,  or  " storm  area/'  or  "low" 
of  the  meteorologist.  It  is  not  destructive  like  the  tornado, 
and  at  times  it  moves  across  the  country  entirely  unnoted 
save  by  the  fall  and  rise  again  of  the  barometer.  As  a  rule 
the  weather  changes  incident  to  its  approach  and  passage 
are  characteristic,  and  may  be  foretold  with  considerable 
degree  of  accuracy  for  a  day  or  two  ahead  of  the  low.  The 
average  eastern  progress  of  the  cyclonic  movement  is  about 
thirty  miles  per  hour. 

SUMMARY 

As  moisture-laden  air  feeds  into  the  rising  air  current  at  the  centre 
of  a  "low,"  the  lessened  density  and  pressure  there  allows  its  expansion. 
The  lowered  temperature  that  results  from  this  expansion  may  at  times 
result  in  cloud  formation  only,  while  at  other  times  there  will  be  more 
or  less  of  precipitation. 


THE  ATMOSPHERE  131 

The  spiral  movement  of  air  upward  around  the  centre  of  a  "low' 
may  be  accounted  for  as  the  result  of  differences  in  the  rate  of  eastward 
motion  of  portions  of  the  earth's  surface  in  different  latitudes.  This 
velocity  varies  from  seventeen  miles  a  minute  at  the  equator  to  a  zero 
value  at  the  poles. 

Wind  directions  in  the  United  States  are  largely  controlled  by  the 
changing  positions  of  the  atmospheric  conditions  known  as  highs  and 
lows  in  their  passage  across  the  country.  In  a  general  way  the  winds 
at  any  point  are  from  a  high  toward  a  low,  and  the  positions  of  these 
highs  and  lows  are  ever  changing. 

The  cyclone  of  the  meteorologist  is  a  condition  of  the  atmosphere, 
not  a  destructive  storm.  The  weather  changes  accompanying  it  may 
at  times  be  very  marked,  and  again  scarcely  noted.  Its  average  rate 
of  progress  eastward  is  about  seven  hundred  miles  in  twenty-four  hours. 

The  heat  equator  is  an  imaginary  line  that  for  sake  of  simplicity 
may  be  considered  as  connecting  all  those  places  where  the  sun's  rays 
are  vertical  as  the  earth  makes  each  day's  rotation.  Such  a  line  con- 
tinued day  after  day  would  be  a  spiral,  extending  as  far  northward  as 
the  Tropic  of  Cancer  on  June  21,  and  as  far  southward  as  the  Tropic 
of  Capricorn  on  or  about  December  21.  This  involves  a  shifting  of 
over  three  thousand  miles  north  and  south  in  six  month's  time.  It 
practically  coincides  with  the  earth's  equator  on  or  about  the  dates 
September  21  and  March  21.  Owing  to  differences  in  altitude  of 
places  along  the  course  of  the  heat  equator,  and  because  of  local  con- 
ditions, any  line  connecting  places  of  highest  temperature  would  be 
very  irregular. 

As  the  northward  moving  upper  atmosphere  gradually  settles  over 
the  North  American  continent  and  comes  to  the  earth's  surface  in  the 
Rocky  Mountain  plateau,  it  may  be  considered  as  still  retaining  more 
or  less  of  its  eastward  motion  acquired  in  the  equatorial  regions.  As 
dry  cold  air,  and  therefore  dense  air,  its  eastward  passage  across  coun- 
try will  be  accompanied  by  relatively  high  barometer  readings,  clear 
skies,  and  cooler  temperatures.  Its  advancing  eastern  edge  may  so 
chill  the  atmosphere  of  any  section  to  which  it  comes  as  to  cause 
cloudiness,  with  possible  precipitation  in  the  form  of  snow. 

Exercises 

1.  What  determines  the  height  at  which  a  column  of  mercury  in  a  barometer 
tube  is  sustained?  Why  would  a  water  column  be  sustained  at  a  greater 
height? 


132  GENERAL  SCIENCE 

2.  What  are  the  twa  common  causes  of  change  in  atmospheric  pressure? 

What  is  the  reason  for  forecasting  rain  when  there  is  a  marked  fall  in  the 
mercury  of  the  barometer? 

3.  What  is  true  (a)  of  the  relative  weights  of  dry  and  moisture-laden  air; 

(b)  of  the  capacity  of  air  to  hold  moisture  as  its  temperature  rises? 
What  are  the  relative  densities  of  water  vapor  and  of  air? 

4.  What  is  meant  by  the  heat  equator?     What  is  its  location  relative  to  the 

earth's  equator?     Account  for  its  shifting  position. 

5.  Discuss  the  conditions  that  give  rise  to  a  more  or  less  constant  "low 
pressure"  along  the  heat  equator. 

6.  What  is  an  explanation  of  the  heavy  rainfall  accompanying  the  migration 
of  the  heat  equator  north  and  south,  and  the  recurrence  of  the  rainy 
seasons  in  the  Tropics?     Under  what  conditions  may  there  be  only  cloud 
formation  as  moisture-laden  air  rises? 

7.  Give  a  possible  explanation  (a)  for  the  origin  of  the  highs;  (b)  for  their  gen- 
erally eastward  motion  across  the  United  States. 

8.  Account  for  the  fact  that  any  wind  moving  northward  in  the  northern 
hemisphere  is  deflected  east  of  north,  becoming  a  southwest  rather  than  a 
south  wind.     In  what  direction  do  winds  in  the  northern  hemisphere  move 
about  a  low  as  regards  the  direction  in  motion  of  clock  hands? 

9.  How  is  the  cooling  of  air  as  it  rises  largely  to  be  accounted  for? 

10.  What  condition  of  atmosphere  is  supposed  to  exist  within  the  funnel  of  a 
tornado?     Why  is  this? 

11.  What  is  a  plausible  explanation  for  the  increase  (or  decrease)  in  violence 
of  a  tornado?     Why  does  a  tornado  after  a  time  cease  to  exist  as  a  destruc- 
tive storm? 

12.  Distinguish  between  a  cyclone  and  a  tornado. 


VI.  WEATHER  AND  CLIMATE 

WEATHER  IN  THE  AFFAIRS  OF  MEN 

It  is  not  at  all  strange  that  comments  upon  the  weather 
should  be  prominent  as  people  exchange  greetings  in  the 
affairs  of  life.  The  advance  of  mankind  from  savagery  to 
civilization  is  intimately  related  to  man's  mastery  of  the 
forces  of  nature.  Not  the  least  of  these  triumphs  have  been 
achieved  in  efforts  to  secure  protection  from  the  weather. 
Among  civilized  peoples  dwellings  are  planned,  built,  and 
furnished  at  relatively  large  expense  in  time,  labor,  and 
materials.  The  cost  of  a  modern  dwelling  of  the  average 
type  of  American  houses  represents  years  of  the  savings  of  a 
wage-earner.  The  annual  outlay  for  necessary  clothing 
for  the  individual  members  of  a  family  is  a  large  drain  upon 
the  average  income. 

The  tiller  of  the  soil  especially  meets  success  or  failure  as 
he  is  favored  by  weather  conditions  or  experiences  losses  on 
account  of  them.  The  complex  machinery  of  modern  life 
becomes  seriously  disordered  when  snow  blockades  or  floods 
stop  railway  traffic  for  a  time,  and  when  communications  by 
telegraph  and  telephone  are  interrupted  by  storms.  The 
total  of  losses  in  great  disasters  due  directly  or  indirectly  to 
the  weather  is,  however,  small  in  comparison  with  the  extent 
of  suffering,  impaired  health,  and  shortened  lives  on  the  part 
of  those  who  by  their  own  incompetency,  or  by  force  of 
circumstances  which  they  cannot  control,  lack  sufficient 
protection  from  the  weather. 


134 


GENERAL  SCIENCE 


Failure  to  take  precautions,  and  to  make  preparations 
against  conditions  of  weather  and  climate  that  are  inevitable, 
is  an  evidence  of  lack  of  thrift  and  foresight,  and, must  result 
in  hardships.  It  is  the  part  of  wisdom  for  everyone  to  avoid 
all  unnecessary  exposure,  and  to  take  all  reasonable  precau- 
tions against  danger  to  health,  life,  and  property.  In  the 
struggles  of  men  for  life  and  comfort  and  prosperity  in  spite 


FIG.   50. — A  house  in  the  Philippines. 

tution.) 


(Courtesy  of  the  Smithsonian  Insli- 


of  adverse  conditions  of  climate,  both  resourcefulness  and 
capability  are  developed.  The  intelligence  and  industry  of 
a  people  are  very  closely  associated  with  these  efforts,  as 
are  their  advances  in  civilization  and  the  stability  of  their 
governments. 

Energy  employed  to  battle  against  unfavorable  weather 
conditions  cannot  be  turned  to  other  uses.  The  efficiency 
of  one's  physical  and  mental  efforts  is  reduced  to  the  extent 
that  his  energy  is  exhausted  or  impaired  by  them. 


WEATHER  AND  CLIMATE  135 

The  benumbing  effects  of  the  cold  of  the  higher  latitudes, 
and  the  enervating  effects  of  heat  and  moisture  in  tropical 
countries,  may  be  named  as  sufficient  cause  for  the  failure 
of  the  peoples  of  these  regions  to  keep  pace  with  the  other 
parts  of  the  world  in  the  arts  and  activities  of  civilized  life. 
However,  the  enterprise  of  the  present  day  has  been  able  to 
master  adverse  climatic  conditions.  This  is  strikingly  ex- 
hibited in  the  Panama  Zone,  Cuba,  and  the  Philippines,  as 
controlled  by  the  United  States,  and  in  portions  of  tropical 
Africa  under  the  enlightened  rule  of  European  nations. 

Aside  from  the  discomforts  of  extreme  heat  or  cold,  exces- 
sive moisture  or  dryness,  and  dangers  from  exposure  to 
weather  changes,  it  is  not  easy  to  establish  definite  relation- 
ships between  weather  conditions  and  the  health  of  people- 
generally.  A  breeze,  springing  up  in  a  hot  day  in  summer 
when  there  has  been  no  air  stirring,  does  for  large  numbers 
of  people  what  starting  an  electric  fan  does  for  the  persons  in 
a  room  whose  hot  stagnant  air  has  become  oppressive  and 
benumbing.  Though  the  temperature  of  the  air  may  remain 
the  same,  perspiration  vaporizes  more  rapidly,-  there  is  a 
lower  body  temperature,  a  lessened  sense  of  discomfort 
and  of  nervous  irritation,  and  an  invigoration  that  bespeaks 
less  waste  of  nerve  energy.  Certain  diseases  have  been 
prevalent  and  often  are  epidemic  at  certain  seasons  of  the 
year.  But  knowledge  of  the  nature  of  infectious  diseases, 
and  of  the  ways  of  their  prevention,  lessens  the  likelihood  of 
any  such  relationship  being  maintained. 

It  is  a  common  experience,  however,  that  the  presence  of 
too  much  moisture  in  the  air  on  a  hot  summer  day  so  interferes 
with  the  rapid  vaporization  of  the  perspiration  from  the  body 
that  great  discomfort  follows.  Heat  prostrations,  especially 
in  sea  board  cities,  are  frequently  the  direct  result  of  the  body 
being  unable  to  get  rid  of  its  own  heat  sufficiently  fast  through 
vaporization  of  perspiration.  Overcrowded  and  poorly  venti- 


136  GENERAL  SCIENCE 

lated  assembly  halls  and  schoolrooms  may  give  to  persons  in 
them  a  feeling  of  discomfort  and  illness  due  to  the  same  cause. 

On  the  other  hand  too  small  an  amount  of  moisture  in  the 
air  dries  the  air  passages  and  skin,  causing  an  irritation  that 
disturbs  the  nervous  equilibrium.  In  our  furnace-heated 
houses  in  winter  time  it  is  possible  by  evaporation  of  water 
at  the  furnace  to  control  the  amount  of  moisture  in  the  air. 
The  humidity  should  range  from  40  to  50  per  cent  of  satura- 
tion1. Too  great  humidity  is  enervating,  and  no  sustained 
physical  or  mental  effort  is  possible.  If  the  air  is  too  dry 
furniture  shrinks,  and  the  mucous  linings  of  the  air  passages 
are  irritated  and  rendered  more  susceptible  to  infection. 

Usually  the  high  following  a  period  of  clouds  and  rainfall 
'brings  air  that  is  clear,  cool,  and  bracing.  One  is  invigorated 
and  stimulated  by  it.  But  for  unknown  reasons  the  round  of 
weather  change  in  the  United  States  incident  to  the  passage 
of  highs  and  lows  across  the  country  is  sometimes  inter- 
rupted. A  high  may  remain  stationary  over  any  section 
for  upwards  of  a  week,  especially  in  summertime,  bringing 
to  that  section  an  unbroken  period  of  clear  skies,  drying  air, 
and  pitiless  sunshine.  From  this  nerve-racking  condition 
the  advent  of  moisture  in  the  atmosphere  brings  relief  and 
refreshment.  Changes  in  diet  and  in  mode  of  life  are  even 
more  important  than  changes  in  clothing  to  withstand  the 
"hot  spells"  in  summer  without  prostration  and  suffering. 

"The  sick  man  from  his  chamber  looks 
At  the  twisted  brooks; 
He  can  feel  the  cool 
Breath  of  each  little  pool; 
His  fevered  brain 
Grows  calm  again, 
And  he  breathes  a  blessing  on  the  rain." 

Longfellow's  Rain  in  Summer. 

1  A  humidity  of  60  to  70  per  cent,  as  commonly  stated  in  text- books, 
would  be  likely  in  cold  weather  to  result  in  condensation  of  vapor  on  win- 
dow panes,  and  on  walls  of  rooms. 


WEATHER  AND  CLIMATE  137 

SUMMARY 

Any  discussion  of  the  weather  takes  account  of  temperature,  humid- 
ity, winds,  precipitation,  and  the  state  of  the  sky  as  to  cloudiness. 
While  the  weather  at  any  place  may  vary  from  day  to  day,  even  from 
hour  to  hour,  the  climate  of  any  region  on  the  other  hand  is  an  average 
of  the  weather  conditions  through  long  periods  of  time,  and  it  changes 
but  little. 

Personal  well-being  and  self  preservation  alike  demand  that  the 
weather  be  taken  into  account  in  the  affairs  of  life.  Making  provision 
against  weather  changes,  and  any  unfavorable  conditions  incident  to 
these  changes,  constitutes  one  of  the  chief  incentives  for  thrift  and 
resourcefulness  in  individuals.  It  is  a  large  factor  in  making  and  main- 
taining the  enlightenment  and  progress  of  nations. 

Suitable  changes  in  diet,  clothing,  and  activities  should  accompany 
changes  in  weather  in  order  to  adjust  the  manner  of  life  to  prevailing 
conditions.  Failure  to  do  this  is  likely  to  involve  waste,  lack  of  effi- 
ciency, and  risks  to  health  and  to  life  itself. 

It  is  likely  that  nervous  temperaments  may  at  times  be  seriously 
affected  by  weather  conditions  unusually  prolonged,  resulting  in  some 
cases  in  depression  of  spirits  and  at  other  times  in  undue  exhilaration. 

Where  the  humidity  of  the  air  is  high  in  summer  there  is  enough  of 
interference  with  the  vaporization  of  perspiration  to  cause  discomfort. 
If  extreme,  this  condition  may  imperil  life  by  an  unduly  high  tempera- 
ture in  the  body.  Heat  prostrations  do  not  necessarily  imply  exposure 
to  the  direct  rays  of  the  sun. 

WTeather  forecasts  to  be  of  value  must  take  into  account  existing 
conditions  over  relatively  large  areas.  They  demand  a  skilled  inter- 
pretation of  these  conditions.  The  forecasts  are  based  upon  "laws" 
of  the  weather,  or  general  statements  concerning  weather  changes. 
These  laws  have  been  verified  from  weather  records  extending  over 
long  periods  of  observation. 

WEATHER  AS  AFFECTED  BY  HIGHS  AND  Lows 

In  the  central  west  of  the  United  States  where  typical 
weather  conditions  due  to  highs  and  lows  are  the  rule,  the 
moisture-laden  winds  may  be  considered  as  coming  from  the 
Gulf  of  Mexico.  They  commonly  enter  the  southeast 


138  GENERAL  SCIENCE 

quadrant  of  a  low.  By  reason  of  the  lessened  pressure  ex- 
perienced in  these  areas  as  the  air  currents  rapidly  ascend 
there  is  an  expansion  of  the  air  and  a  consequent  cooling  of 
it.  The  skies  are  beclouded  and  some  of  the  moisture  may 
be  precipitated  as  snow  or  rain.  On  the  other  hand  the 
cool  dry  air  from  the  north  and  northwest  brings  clear  skies 
and  bright  sunshine. 

As  an  easterly  moving  area  of  low  pressure,  or  cyclone, 
approaches  and  passes  an  observer  so  that  successively  he  is 
in  its  eastern  edge,  then  in  its  central  portions,  and  then  in 
its  western  edge,  a  certain  succession  of  weather  changes 
is  likely  to  occur.  Regardless  of  the  rate  of  the  eastward 
movement  of  the  storm  area  and  the  length  of  time  required 
for  the  round  of  changes,  the  order  in  which  these  changes 
occur,  and  their  characteristics,  will  be  somewhat  as  follows: 

1.  While   in   the   eastern   edge,    an   increasing   cloudiness 
culminating  in  more  or  less  of  precipitation;  a  rising  tem- 
perature; winds  from  the  southeast,  and  south. 

2.  While  in  the  central  portion,  cloudiness  and  rain   (or 
snow)   continued;  little  or  no  wind;  relatively  high  tem- 
perature. 

3.  While  in  the  western  portion,  cloudiness  gives  way  to 
clear   skies;  winds  from  northwest,  and  west;  lower  tem- 
peratures (cooler). 

When  the  area  of  low  pressure  passes  to  the  northward, 
there  is  a  typical  succession  of  changes  experienced  by  the 
observer  while  enveloped  in  turn  by  the  southeast,  south, 
and  southwest  portions  of  the  storm  area.  These  changes 
are  commonly  (a)  an  increasing  cloudiness,  more  or  less  of 
precipitation,  and  a  rising  temperature;  (b)  a  change  of 
wind  direction  from  southeast  through  the  south  to  the  west, 
with  the  skies  clearing,  and  a  lower  temperature. 

When  the  storm  area  passes  to  the  south  of  an  observer 
the  wind  directions  change  from  easterly  through  the  north 


WEATHER  AND  CLIMATE  139 

to  northwesterly  winds,  and  there  is  a  succession  of  cloudi- 
ness and  possible  precipitation  followed  by  clearing  skies, 
the  winds  from  the  north  being  cool.  The  rate  at  which 
the  changes  occur,  and  the  intensity  of  the  storm,  is  fore- 
casted by  the  rapidity  and  extent  of  fall  of  the  mercury  in 
the  barometer. 

During  the  summer  the  paths  of  the  lows  across  the  United 
States  are  likely  to  be  farther  to  the  north,  and  in  winter 
farther  to  the  south.  For  an  observer  in  any  one  place  there 
is  likelihood  of  a  repetition  in  summer  of  warm  winds  from  a 
southerly  direction,  and  in  winter  of  cold  winds  from  a 
northerly  direction. 

Some  or  many  of  these  features  of  weather  changes  may 
be  absent  in  the  passing  eastward  of  any  cyclonic  area, 
and  the  intensity  of  these  features  may  vary  widely.  But  so 
largely  are  they  characteristic  of  cyclones  that  without  re- 
course to  weather  maps  and  barometers  close  observers  of 
changes  in  the  appearance  of  the  sky,  in  the  directions  of  the 
wind,  and  in  thermometer  readings,  are  able  to  foretell 
weather  changes  somewhat  accurately.  The  direction  of 
the  centre  of  any  area  of  low  pressure  from  an  observer  will 
in  general  be  somewhat  to  the  left  of  the  direction  toward 
which  the  wind  is  blowing. 

SUMMARY 

The  advancing  edge  of  a  low  commonly  brings  to  each  region  over 
which  it  passes  more  or  less  of  cloudiness  and  of  precipitation.  Where 
this  occurs  it  may  be  explained  as  due  to  an  expansion  of  the  moisture- 
laden  air  passing  into  the  low.  By  reason  of  this  expansion  the  tem- 
perature of  the  air  is  lowered  sufficiently  to  condense  more  or  less  com- 
pletely the  moisture  it  contains. 

When  the  low  has  passed  on  eastward  across  the  United  States  the 
westerly  winds  blowing  toward  it  are  relatively  cool  and  dry,  coming 
as  they  do  over  the  central  continental  areas  northward  into  Canada. 
As  these  winds  become  warmed  from  the  regions  over  which  they  pass 


I4o  GENERAL  SCIENCE 

their  capacity  for  moisture  increases,  and  clouds  disappear  as  result 
of  the  vaporization  of  the  water  particles  forming  the  clouds. 

The  paths  traversed  by  the  centres  of  these  areas  of  low  pressure  on 
their  eastward  journeys  across  country  generally  range  farther  north 
in  summer,  and  much  to  the  southward  in  winter.  This  results  in 
weather  changes  far  more  varied  than  would  be  true  if  dependent  only 
upon  the  approach  of  storm  areas  from  the  west  and  their  passing  on 
eastward. 

The  isotherms  on  weather  maps  connect  places  reporting  the  same 
temperatures.  Isobars  connect  places  having  the  same  atmospheric 
pressure  as  shown  by  barometer  readings. 

So  numerous  are  variations  from  the  general  rules  of  weather  that 
no  brief  summarization  of  weather  conditions  is  at  all  adequate.  Local 
conditions  are  often  large  factors  in  the  weather  of  any  particular  sec- 
tion. "As  fickle  as  the  weather"  does  not,  however,  signify  that  the 
great  controlling  causes  of  the  weather  may  not  in  a  general  way  be 
understood  by  those  who  have  made  no  extended  study  of  Meteorology. 


Exercises 

1.  What  distinction  is  made  in  the  use  of  the  terms  weather  and  climate? 

2.  What  besides  total  annual  amount  is  important  in  the  relation  of  rainfall 
to  the  raising  of  crops? 

3.  What  geographic  conditions  make  winds  from  the  north  and  northwest  in 
the  interior  of  this  continent  of  lower  humidity? 

4.  Name  several  ways  in  which  men  protect  themselves  from  unfavorable 
weather  conditions. 

6.  Contrast  the  exposure  incident  to  occupations  and  travel  now  and  in 
earlier  generations. 

6.  To  what  extent  can  man  control  the  weather? 

7.  Explain  the  clearing  of  the  sky  and  the  cooler  weather  when  a  low  moves 
on  eastward,  and  northwesterly  winds  spring  up. 

8.  In  what  ways  do  winds  affect  the  well-being  of  mankind  ? 

9.  Trace  any  apparent  relationship  between  climate  and  the  civilization  of 
any  people. 


THE  THERMOMETER,  AND  HEAT  TRANSMISSION 

Changes  in  the  volume  of  a  body  by  reason  of  its  being 
heated  or  cooled  are  proportional  to  the  changes  in  its'tem- 


WEATHER  AND  CLIMATE  141 

perature1.  So  generally  is  it  true  that  heating  a  body  causes 
it  to  increase  in  size,  and  cooling  it  causes  shrinkage  in 
volume,  that  any  exception  might  be  wholly  disregarded. 
But  the  peculiar  behavior  of  water  must  not  pass  unnoticed. 
As  water  is  cooled  more  and  more  it  shrinks  in  its  volume, 
as  might  be  expected,  till  a  temperature  of  about  4°  C.  is 
reached.  Further  cooling  results  in  its  expanding  till  it 
changes  to  ice.  As  previously  noted  there  are  many  in- 
stances of  increase  in  volume  where  change  from  liquid  state 
to  solid  occurs,  but  water  when  cooled  begins  to  expand  while 
yet  several  degrees  above  the  freezing  temperature.  This 
makes  4°  C.  the  temperature  of  maximum  density  for  water, 
and  any  change  from  that  temperature,  whether  rise  or  fall, 
involves  increase  in  its  volume. 

The  amount  of  expansion  (and  of  contraction)  is  relatively 
small  in  solids,  is  more  in  liquids,  and  is  relatively  large  in 
gases.  Every  substance  has  its  own  so-called  coefficient  of, 
expansion.  This  fractional  number  is  found  by  dividing  the 
increase  (or  decrease)  in  size  for  one  degree  temperature 
change  by  the  size  before  the  change  in  temperature  was 
made.  In  dealing  with  gases  the  pressure  under  which  they 
are  confined  must  be  kept  constant,  and  the  volume  of  the 
gas  at  the  freezing  temperature  of  water  (o°  C.)  is  the  basis 
for  comparison  (division). 

The  coefficient  of  expansion  for  mercury  is  sufficiently 
small  so  that  in  the  large  tubes  of  barometers  any  rise  and 
fall  of  the  mercury  column  by  reason  of  temperature  changes 
of  several  degrees  may  be  considered  a  negligible  value  for 
all  general  purposes.  Thermometer  tubes,  however,  have 
an  exceedingly  small  bore.  The  difference  in  levels  of  the 

1  For  the  heat  of  vaporization  and  of  fusion,  where  changes  of  solids  and 
liquids  and  gases  from  one  state  to  another  are  considered,  see  page  95. 
Neither  change  in  volume  by  reason  of  change  of  state,  nor  consideration  of 
any  heat  liberated  or  made  latent  in  any  such  changes,  is  involved  in  studies 
of  the  thermometer. 


142  GENERAL  SCIENCE 

mercury  in  them  at  the  boiling  and  freezing  temperatures  of 
water,  even  when  divided  into  100  (or  180)  equal  parts, 
gives  spaces  (degrees)  sufficiently  long  to  be  easily  read. 
Fractional  portions  of  these  spaces  may  be  estimated  to  the 
tenths  of  a  degree. 

Mercury  has  other  advantages  for  use  in  thermometers. 
It  does  not  cling  to  the  glass  as  does  water  and  other  liquids. 
Hence  its  rise  and  fall  is  not  interfered  with  by  adhesive 
force.  Its  boiling  point  of  350°  C.,  and  its  freezing  tempera- 
ture of  —39°  C.,  make  it  serve  for  all  ordinary  temperature 
changes.  For  temperatures  either  very  high  or  very  low 
special  forms  of  thermometers  are  employed,  descriptions  of 
some  of  which  are  commonly  given  in  Physics.  Then,  too, 
the  coefficient  of  expansion  of  mercury  is  very  nearly  con- 
stant, the  mercury  not  expanding  appreciably  more  per 
degree  temperature  change  in  one  part  of  the  scale  than  in 
another  part. 

When  a  confined  gas  at  o°  C.  has  its  temperature  raised  or 
lowered  one  degree,  and  the  pressure  to  which  it  is  subjected 
is  kept  the  same  all  the  time,  it  is  found  that  the  increase  or 
decrease  in  its  volume  is  always  J^73  of  the  volume  at  op  C. 
If  the  temperature  is  changed  20°  then  the  expansion  or  con- 
traction is  2%73  of  that  volume.  "  If  then  a  gas  could  be 
cooled  to  a  temperature  of  —273°  C.,  and  it  still  remained  a 
gas,  its  volume  theoretically  would  become  zero.  Such  a  tem- 
perature is  assumed  to  exist,  and  it  is  called  absolute  zero. 
Temperatures  in  the  centigrade  scale  are  changed  to  absolute 
readings  by  adding  273  to  their  centigrade  values. 

To  the  scientist  this  possible  temperature  has  the  greatest 
interest.  Within  recent  years  temperatures  approximating  ab- 
solute zero  have  been  attained  in  physical  laboratories.  The 
story  of  how  this  has  been  done,  and  of  the  changes  that  take 
place  in  the  nature  of  substances  subjected  to  these  tempera- 
tures, adds  an  interesting  chapter  to  the  study  of  Physics. 


WEATHER  AND  CLIMATE  143 

When  coal  or  wood  is  burned  in  a  stove,  the  warmth  (heat) 
liberated  as  a  result  of  combustion  is  disseminated  in  three 
different  ways.  The  stove  itself  becomes  heated  largely  by 
conduction.  In  such  cases  the  heat  travels  from  molecule 
to  molecule  till  distributed  throughout  the  body  that  is 
heated.  It  is  believed  that  in  the  conduction  of  heat  in  a 
body  a  quickening  of  molecular  motion  is  passed  on  through 
it,  and  the  degree  of  this  molecular  activity  manifests  itself 
in  the  rising  temperature  at  different  places  outward  from 
where  the  liberation  or  application  of  heat  occurs.  This 
belief  is  in  accordance  with  the  molecular  theory  of  the 
structure  of  matter,  and  makes  possible  the  definition  that 
heat  is  molecular  energy. 

From  a  stove  as  a  center  convection  currents  are  set  up  as 
the  air  next  the  hot  surface  is  warmed  and  expanded,  and  a 
circulation  of  air  is  maintained.  (See  pages  20  and  123.) 
A  hot-air  furnace  is  essentially  a  large  stove  located  com- 
monly in  the  basement  and  surrounded  by  a  metal  jacket 
from  which  large  sheet-metal  pipes  convey  heated  air  as 
convection  currents  direct  to  the  rooms  to  be  warmed. 
Into  the  space  between  jacket  and  furnace  cold  air  is  con- 
veyed directly  from  out-of-doors,  or  more  commonly 
through  cold- air  pipes  from  the  various  rooms  to  which  the 
heated  air  rises,  thus  completing  a  round  of  circulation  of  air 
in  these  rooms.  In  part  at  least  this  air  may  be  warmed 
many  times  over. 

Unequal  heating  of  the  rooms  of  a  house  from  use  of  a  hot- 
air  furnace  sometimes  results  by  reason  of  the  fact  that 
heated  air  cannot  rise  through  the  hot-air  pipes  into  any 
room  from  which  the  cold  air  is  unable  to  escape  freely 
through  openings  of  sufficient  size.  Distribution  of  the 
heated  air  to  different  rooms  in  a  house  may  be  controlled  by 
use  of  dampers  in  the  hot-air  pipes. 

In  hot-water  heating  plants  the  heat  liberated  at  a  furnace 


144  GENERAL  SCIENCE 

in  the  basement  sets  up  convection  currents  in  water  that 
fills  pipes  within  the  furnace,  and  radiators  in  the  rooms 
to  be  heated,  and  the  connecting  pipes.  The  heated  water 
goes  from  furnace  to  radiator,  and  then  as  cooled  water  from 
the  radiators  back  to  the  furnace  to  be  warmed  anew.  In 
steam-heating  plants  and  in  vapor  systems  the  essential 
difference  from  the  hot- water  system  is  in  having  the  pipes 
filled  with  steam  or  water  vapor,  the  heat  liberated  at  the 
radiators  being  largely  heat  of  vaporization  (latent  heat) 
from  the  steam  as  it  condenses  to  water  in  the  radiators. 
Where  there  are  pipes  to  carry  the  steam  to  the  radiators, 
and  other  pipes  to  carry  away  the  water  of  condensation, 
there  is  little  or  none  of  the  disagreeable  " bumping"  that 
often  occurs  when  steam  is  entering  a  radiator  from  which 
water  is  draining  back  to  the  boiler  through  the  same  pipe. 

Conduction  and  convection  are  modes  of  transmission  of 
heat  by  reason  of  molecular  activity  in  matter.  But  heat 
can  pass  through  space  destitute  of  matter,  even  through  a 
vacuum.  Heat  from  the  sun  reaches  the  earth  through  vast 
spaces  supposed  to  be  lacking  in  any  material  medium  for  its 
transmission.  Scientists  assume  that  heat  requires  some 
medium  in  which  it  can  pass  through  space.  It  is  assumed 
to  be  the  case  that  heat,  light,  and  other  forms  of  energy 
(see  pages  162  and  343)  are  transmitted  through  space  as 
pulsations  (wave  motions)  in  a  so-called  "ether"  medium, 
and  that  these  pulses  move  outward  or  radiate  in  every 
direction  and  always  in  straight  lines.  Such  a  supposition 
has  sufficient  experimental  evidence  supporting  it  to  make 
it  the  most  reasonable  of  all  explanations  of  heat  radiation. 

However,  this  " radiant  energy"  is  not  heat  until  the  ether 
waves  fall  upon  some  body  whose  molecules  acquire  a  quick- 
ened motion  by  reason  of  the  absorption  of  the  motion  of  the 
ether  medium.  In  this  way  the  temperature  of  the  body  is 
raised  as  ether  energy  is  transformed  into  molecular  motion 


WEATHER  AND  CLIMATE  145 

or  heat.  The  warmed  body  in  turn  may  lose  this  energy  of 
its  molecules  by  conduction  to  other  bodies,  by  convection 
currents,  and  by  radiations  from  itself  as  an  original  source. 

Some  substances  are  much  better  conductors  of  heat  than 
others.  Some  conduct  heat  so  slowly  as  to  be  called  non- 
conductors. In  fireless  cookers  the  space  between  the 
double  walls  is  filled  in  with  asbestos,  felt,  or  some  like  non- 
conducting material,  thus  preventing  the  loss  outward  of  the 
heat  (molecular  motion)  of  the  material  put  into  the  inner 
receptacle.  This  permits  the  softening  process,  or  "cook- 
ing'7 of  any  foodstuff  to  continue  for  a  long  time  after  the 
heated  material  has  been  properly  packed  away  in  the 
cooker.  The  fireless  cooker  may  likewise  be  used  to  keep 
things  cool  in  summer  by  keeping  out  the  heat  of  the  surround- 
ing air.  Icehouses  are  constructed  on  the  same  principle, 
the  space  between  their  double  walls  being  packed  with  some 
cheap  non-conducting  material  such  as  saw-dust,  thus  pre- 
venting heat  from  without  reaching  and  melting  the  ice. 

Refrigerators  for  household  use,  fire-proof  safes,  and 
vaults  for  storage  of  business  papers  and  other  valuables 
are  built  with  double  walls  filled  with  non-conducting 
material  of  some  kind.  In  " thermos  bottles"  air  was 
withdrawn  from  between  the  double  walls  of  glass,  and  that 
space  was  then  sealed  air-tight  by  melting  off  the  tubular 
outlet  of  glass.  Transmission  of  heat  either  inward  or  out- 
ward through  this  vacuum  is  thus  made  impossible  by  either 
conduction  or  convection.  The  jacket  of  hot-air  furnaces, 
and  the  pipes  carrying  heated  air  from  the  furnace  to  the 
rooms  to  be  warmed,  are  covered  commonly  with  thin 
sheets  of  asbestos  to  lessen  wastage  of  heat  in  its  trans- 
mission. Steam  and  hot-water  pipes  are  protected  "from 
the  cold"  in  some  like  manner. 

It  is  to  be  remembered  that  the  rise  of  heated  air  through 
the  smoke  pipe  and  chimney,  constituting  the  "draft"  of  a 


146  GENERAL  SCIENCE 

stove  or  furnace,  represents  a  waste  of  heat  liberated  in  the 
combustion  of  the  fuel  used.  While  much  of  this  waste  is 
incident  to  the  maintenance  of  an  oxygen  supply  for  keeping 
up  combustion,  it  is  possible  to  so  regulate  the  dampers  of 
a  heating  outfit  by  frequent  adjustments  as  to  keep  the 
waste  of  heat  and  of  its  fuel  equivalent  at  a  minimum. 
The  heat  in  the  water  drawn  from  reservoir  or  boiler  at  a 
kitchen  range  may  be  heat  saved  rather  than  lost  up  the 
chimney.  In  the  use  of  gas  ranges,  too,  a  careful  regulation 
of  the  flow  of  gas  will  save  much  unnecessary  expense. 
After  water  that  is  being  heated  has  begun  boiling  it  cannot 
be  made  any  hotter  when  in  an  open  dish.  To  keep  it  boiling 
thereafter,  only  enough  heat  is  needed  to  replace  what  is 
being  carried  off  in  the  escaping  vapor. 

SUMMARY 

Temperature  means  degree  of  heat.  It  is  entirely  independent  of 
the  quantity  of  matter  in  the  body,  but  is  proportional  to  the  rate  of 
motion  of  the  molecules  of  the  body.  Heat  in  a  body  is  the  energy  it 
possesses  by  reason  of  its  molecular  motions. 

The  measurement  of  temperature  is  based  upon  the  principle  that 
changes  in  volume  of  a  body  are  proportional  to  temperature  changes. 
It  is  assumed  that  expansion  takes  place  at  the  same  rate  as  the  rise 
in  temperature.  As  the  molecular  motion  decreases  shrinkage  in  vol- 
ume and  lowering  of  temperature  occur  at  the  same  rate. 

The  coefficient  of  expansion  is  the  fraction  showing  what  part  of  an 
original  length,  surface,  or  volume  a  body  increases  per  degree  rise  in 
temperature.  For  solids  and  liquids,  it  varies  with  the  substance;  for 
all  gases,  when  based  upon  the  gaseous  volume  at  o°  C.,  it  is  ^73  of 
that  volume  per  degree  centigrade,  or  Y±§\  per  degree  Fahrenheit. 

Mercury  has  many  properties  adapting  it  for  use  in  temperature 
measurements.  Enclosed  within  a  sealed  glass  tube  it  is  readily  seen 
through  the  glass.  Its  rise  and  fall  is  not  interfered  with  by  any  adhe- 
sion to  the  glass.  The  wide  range  in  temperature  between  the  freezing 
and  boiling  points  of  mercury  covers  all  ordinary  uses  of  thermometers. 
Its  specific  heat,  i.e.,  the  amount  of  heat  necessary  to  change  its  tern- 


WEATHER  AND  CLIMATE  147 

perature  one  degree,  is  so  small  that  its  change  in  volume  when 
confined  in  a  small  tube  is  apparent  when  the  total  quantity  of  heat 
involved  is  relatively  small.  At  the  same  time  the  coefficient  of  ex- 
pansion is  so  small  that  a  short  tube  only  is  needed  for  its  increase 
in  volume  from  the  freezing  to  the  boiling  temperature  of  water. 

From  the  coefficient  of  %7B  for  the  expansion  (or  contraction)  of 
gases,  a  thermometer  scale  has  been  devised  having  degrees  of  the  same 
value  as  those  of  the  centigrade  scale,  but  a  zero  273  centigrade  degrees 
below  the  zero  of  the  centigrade  scale.  Much  use  of  this  "absolute" 
scale  is  made  by  scientists. 

Heat  passes  outward  from  any  place  where  it  is  set  free  either  by 
conduction  or  convection  in  a  material  medium  (solid,  liquid,  or  gaseous 
bodies),  or  by  means  of  waves  radiating  outward  through  an  ether 
medium. 

Where  bodies  cool  (lose  heat)  other  than  by  conduction  or  convection, 
it  may  be  supposed  their  molecular  energy  or  heat  is  used  up  in  origi- 
nating ether  impulses  or  wave  motions  that  pass  off  into  surrounding 
space.  These  in  their  turn  may  fall  upon  some  body  whose  molecular 
motion  is  quickened  by  the  " absorption"  of  the  ether  motion,  the 
body  thus  becoming  warmed.  This  transformation  of  ether  motion 
into  molecular  motion,  or  heat,  is  involved  in  the  absorption  by  bodies 
of  light  and  other  forms  of  radiant  energy. 

Bodies  may  be  kept  hot,  or  "kept  cold",  by  enclosing  them  in  spaces 
more  or  less  free  of  air,  or  by  filling  confined  air  spaces  with  material 
that  neither  conducts  nor  conveys  heat  readily. 

SOLAR  HEATING 

The  angular  difference  in  direction  of  two  lines  from  an 
observer  at  any  time,  one  directly  upward  (vertical)  and  one 
toward  the  sun,  may  be  considered  as  the  obliquity  of  the 
sun's  rays  at  that  particular  time.  This  value  is  expressed 
in  degrees.  If  the  sun  at  the  time  is  halfway  down  from  the 
zenith  (point  directly  overhead)  to  the  horizon,  the  obliquity 
of  the  sun's  rays  is  45°.  When  the  sun  is  at  the  horizon,  the 
angle  is  90°.  Heat  and  light  from  the  sun  then  may  be  con- 
sidered as  passing  across  the  surface  of  the  earth  where  the 
observer  is  without  being  stopped  by  the  earth's  surface. 


148 


GENERAL  SCIENCE 


The  obliquity  of  the  sun's  rays  from  its  rising  to  setting 
changes  from  90°  in  the  morning  to  a  minimum  value  when 
on  meridian  (solar  noon),  and  then  to  90°  again  when  it  sets. 
It  will  be  found  by  continued  observations  that  this  daily 
path  varies  in  points  of  rising  and  setting,  and  in  meridian 
altitude  (number  of  degrees  up  from  the  south  point  of 
horizon  at  noontime).  Changes  in  the  diurnal  circles  of  the 
sun  relative  to  our  horizon  are  the  result  of  the  revolution  of 
the  earth  about  the  sun.  Any  complete  understanding  of 
these  changes  requires  the  study  of  Astronomy. 


FIG.  51. — Relation  of  solar  heating  to  altitude  of  the  sun.  An  illustration 
of  the  teaching  that  the  more  nearly  vertical  the  sun's  rays  the  more  restricted 
the  area  heated  by  a  solar  beam  of  any  given  cross-section,  and  the  more 
intense  the  heating  effect. 

It  is  not  at  all  difficult  to  imagine,  especially  during  the 
month  of  June  every  year,  that  if  the  sun  continued  after 
June  21  to  rise  farther  and  farther  north  of  east,  and  to  set 
farther  and  farther  north  of  west,  there  would  come  a  time 
when  the  sun  neither  set  nor  rose.  Its  diurnal  circles  would 
remain  continuously  above  the  horizon.  We  are  taught  in 
astronomical  geography  that  an  observer  within  23^°  of  the 
poles  of  the  earth  (inside  the  Polar  Circles)  may  witness  the 
sun  continuously  above  the  horizon  for  days  at  a  time;  that 
at  the  poles  this  time  of  continuous  sunlight  (absence  of  night- 
time) must  be  somewhat  more  than  six  months  in  duration. 


WEATHER  AND  CLIMATE  149 

What  days  of  continuous  sunlight  would  mean  for  us  in  our 
latitudes,  especially  in  summer  with  the  sun  high  up  in  the 
heavens  at  noon,  is  easily  imagined.  With  the  sun  shining 
down  steadily,  even  though  clouds  might  at  times  give  some 
relief,  the  heat  would  be  intolerable  and  destructive. 

However,  in  the  polar  regions  the  elevation  of  the  sun  above 
horizon  cannot  at  any  time  exceed  23^°.  As  a  result  of  this 
low  altitude  the  heat  intensity  is  small,  the  area  covered  by 
a  sunbeam  of  any  cross-section  being  relatively  very  large. 
In  a  similar  manner  in  our  latitude  the  increasing  obliquity 
of  the  sun's  rays  from  about  September  21  each  year  through 
the  three  succeeding  months  results  in  decreased  insolation 
(solar  heating) ,  and  the  coming  on  of  winter.  For  a  long  time 
after  March  21  the  increasing  amount  of  heat  received  does 
not  become  sufficient  to  maintain  plant  growth.  It  is  to  be 
mentioned  in  this  connection,  too,  that  the  more  obliquely 
heat  and  light  fall  upon  any  surface  the  larger  is  the  portion 
of  both  reflected.  Such  reflected  heat  is  lost  so  far  as  warm- 
ing the  earth's  surface  is  concerned. 

SUMMARY 

By  the  obliquity  of  the  sun's  rays  is  meant  their  slant,  or  departure 
from  being  directly  overhead.  This  obliquity  is  measured  in  degrees. 

The  periods  of  continuous  sunshine  within  the  Polar  Circles  range 
from  twenty-four  hours  to  six  months  according  to  nearness  to  the 
Poles.  But  these  periods  of  unbroken  sunlight,  and  of  entire  lack  of 
darkness  save  for  clouds  and  storms,  does  not  result  in  temperatures 
sufficiently  high  to  banish  the  cold  of  either  of  the  Frigid  Zones.  So 
low  down  upon  the  horizon  is  the  sun  during  the  long  polar  day  that 
the  intensity  of  the  solar  heat  is  small.  Then,  too,  of  this  heat  the 
larger  portion  is  reflected  because  of  the  great  obliquity  of  the  rays, 
leaving  but  little  to  be  absorbed  to  warm  the  earth. 

Exercises 

1.  What  causes  the  rise  and  fall  of  the  mercury  in  (a)  thermometers;  (b) 
barometers? 


150  GENERAL  SCIENCE 

2.  Calculate  the  values  in  centigrade  readings  of  (a)  77°F.;  (b)  59°  F.;  (c) 

212°  F.;  (d)  140°  F. 

3.  Calculate  the  values  in  Fahrenheit  degrees  of  (a)  100°  C.;  (b)  30°  C. 

4.  At  what  temperature  does  mercury  (a)  boil;  (b)  freeze?      For  very  low 
temperatures,  as  in  the  polar  regions,  what  liquid  is  used  in  place  of  mer- 
cury for  thermometers? 

5.  State  what  scientists  believe  true  concerning  (a)  the  nature  of  heat  in 
bodies;  (b)  the  cause  of  differences  in  the  temperature  of  bodies. 

6.  Distinguish  between  conduction  and  convection  of  heat  in  matter. 

7.  Where  heat  passes  through  space  destitute  of  matter,  what  is  the  accepted 
teaching  concerning  its  manner  of  transmission  ?     What  is  the  name  given 
the  supposed  medium  that  transmits  the  motion? 

8.  What  is  the  distinction  in  meanings  of  the  terms  reflection,  transmis- 
sion, and  absorption  of  heat. 

9.  Where  light  or  heat  waves  fall  very  obliquely  upon  a  land  or  water  surface, 
what  becomes  of  the  larger  portion  that  evidently  is  not  absorbed  since 
it  does  not  warm  them?     What  is  true  of  the  amounts  absorbed  by  land 
surfaces  as  compared  with  water  surfaces? 


VII.  MATTER  AND  FORCE 

SOME   PROPERTIES  OF  MATTER,  AND  CHANGES  IN  MATTER 
DUE  TO  FORCE 

To  spend  time  watching  the  flames  of  a  bonfire,  or  the  dis- 
appearance of  burning  material  in  a  stove  or  furnace,  is  a 
common  experience.  Wherever  matter  disappears  in  flame 
before  our  eyes,  the  thoughtful  mind  wonders  at  the  evidence 
of  some  mysterious  agency  actively  at  work.  There  is 
something  fascinating  in  watching  even  the  burning  of  a 
match  stick,  something  awe-inspiring  in  witnessing  a  great 
conflagration  when  a  city  is  fire-swept.  It  is  little  wonder 
that  the  ancients  regarded  fire  as  one  of  the  natural  elements, 
and  we  sometimes  speak  now  of  destruction  by  fire  and  flood 
as  work  of  "the  elements." 

Only  an  elementary  knowledge  of  Chemistry  is  needed  to 
understand  that  the  burning  of  substances,  as  we  commonly 
witness  it,  is  but  the  process  of  their  oxidation,  or  union  with 
oxygen.  The  products  of  this  combustion  are  largely  gases 
and  vapors  which  ordinarily  pass  off  into  the  air  unobserved. 
To  explain  the  changes  that  occur  before  our  eyes,  we  rest 
satisfied  with  the  statement  that  they  result  from  the  action 
of  chemical  force,  but  what  this  "  force"  is  we  do  not  under- 
take to  say.  The  most  that  can  be  taught  of  it  has  to  do 
with  the  conditions  under  which  it  manifests  itself,  and  the 
products  of  its  action.  With  these  the  study  of  Chemistry 
is  largely  concerned. 

Living  matter   has   the  distinguishing  characteristics  of 


152  GENERAL  SCIENCE 

spontaneous  motion,  of  growth  by  cell  division,  and  of  repro- 
duction. These  activities  are  seen  in  plants  and  animals. 
Lacking  these  manifestations,  matter  is  lifeless.  The  bio- 
logical sciences  are  those  largely  concerned  with  studies  of 
living  bodies,  while  the  physical  sciences  deal  with  the 
phenomena  of  matter  apart  from  manifestations  of  life  in  it. 
This  distinction,  however,  is  an  arbitrary  one  for  the  purpose 
of  grouping  scientific  knowledge  into  convenient  fields  for 
study.  In  General  Science  no  regard  need  be  paid  to  these 
distinctions. 

Whatever  the  changes  through  which  matter  may  pass, 
two  characteristics  are  maintained — it  always  occupies  space, 
and  its  mass  (quantity  of  matter)  remains  unchanged. 
While  no  one  knows  how  matter  originated,  it  is  fully 
believed  that  there  is  no  destruction  of  matter  in  the  many 
changes  to  which  it  is  subject.  It  is  believed,  too,  that  there 
is  no  creation  of  any  matter,  though  newly  formed  substances 
(kinds  of  matter)  take  the  places  of  those  that  have  disap- 
peared. And  it  is  through  these  changes  occurring  in 
matter  that  we  learn  about  force. 

The  study  of  Physics  is  concerned  with  the  innumerable 
changes  occurring  everywhere  about  us  as  result  of  so-called 
physical  forces.  In  these  changes  the  nature  of  the  matter 
involved  remains  the  same.  Any  "explanation"  of  these 
changes  consists  very  largely  of  statements  of  what  these 
results  are,  and  what  conditions  affect  the  changes.  That 
these  statements  be  clear  and  exact,  it  is  necessary  to  use 
terms  with  some  degree  of  scientific  accuracy.  Indeed,  in 
learning  the  elementary  and  fundamental  facts  concerning 
the  physical  forces  and  their  phenomena1,  there  is  the  best  of 
opportunity  to  acquire  accuracy  of  statement  together  with 

1  Any  change  in  matter,  however  simple  and  familiar,  is  a  phenomenon. 
In  popular  language  the  use  of  the  term  often  implies  that  which  is  unusual 
and  striking. 


MATTER  AND  FORCE 


153 


clearness  and  conciseness  of  expression1.  This  is  necessary 
in  formulating  definitions  of  the  properties  of  matter  such 
as  these: 

Density  of  matter  refers  to  the  compactness  of  its  molecules,  or  the  amount 
of  matter  in  a  given  space. 

Size,  or  volume,  refers  to  the  amount  of  space  occupied  by  a  body. 

Impenetrability  is  the  property  that  does  not  permit  two  bodies  to  occupy 
the  same  space  at  the  same  time. 


FIG.  52. — Masses  the  same  as  shown  by  the  position  at  O  of  the  movable 
arm  Pt  but  densities  different. 

Extension  is  the  property  manifest  in  the  fact  that  a  body  does  occupy 
space. 

Form  results  from  a  limitation  of  the  extension  of  a  body  in  different  direc- 
tions. If  matter  extended  outward  indefinitely  it  would  be  without  form. 
There  would  then  be  no  separated  portions  of  matter,  or  bodies. 

Mobility  refers  to  the  fact  that  bodies  are  movable,  i.e.,  they  can  be  made  to 
change  positions. 

1  From  simple  experiments  performed  in  Physics  it  is  possible  to  acquire 
groups  of  facts  which  call  for  discrimination  in  the  use  of  words  to  express  what 
has  been  learned.  Loose  use  of  language,  and  the  incomplete  indefinite  grasp 
of  facts  usually  accompanying  any  such  use,  defeat  one  of  the  most  important 
purposes  in  the  study  of  high  school  sciences.  On  the  other  hand,  an  ability  to 
repeat  the  carefully  chosen  words  of  a  text-book  in  science  is  no  proof  of  a  full 
understanding  of  their  meaning.  Wrong  notions,  or  imperfect  ones,  obtained 
from  a  misinterpretation  of  the  readings  of  a  text  are  not  easily  corrected  when 
once  acquired.  Special  effort  should  be  made  in  all  studies  in  elementary 
science  for  a  right  choice  and  use  of  terms,  and  for  a  definiteness  in  knowledge 
concerning  what  is  expressed  in  these  words.  One  of  the  valuable  results 
of  wisely  chosen  laboratory  exercises  is  the  acquisition  of  a  vocabulary  of  exact 
scientific  terms  expressive  of  what  has  been  learned  through  experimental 
effort. 


154  GENERAL  SCIENCE 

Inertia  as  another  of  the  properties  of  matter  refers  to  the 
fact  that  bodies  at  rest  cannot  set  themselves  in  motion,  and 
that  when  in  motion  they  cannot  stop  themselves.  A  body 
in  motion  presupposes  some  force  having  acted  upon  the  body 
to  cause  the  motion.  On  the  other  hand  it  is  a  matter  of 
common  experience  to  note  that  moving  bodies  come  to  rest. 
Whatever  their  tendency  to  keep  moving,  i.e.,  their  inertia 
as  moving  bodies,  they  are  brought  to  rest  after  a  time  by 
reason  of  some  form  of  resistance  experienced  by  them  when 
moving. 

Only  as  sufficient  force  is  applied  to  make  good  the  loss  of 
energy  as  a  moving  body  does  work  in  overcoming  resist- 
ance will  the  motion  of  that  body  be  maintained.  This 
resistance  may  be  that  of  friction  developed  as  one  surface 
slides  upon  another;  or  the  resistance  of  medium  as  when  a 
body  moves  through  the  air,  or  through  a  liquid  or  a  solid; 
or  it  may  be  due  to  the  opposing  action  of  some  other  force. 

That  the  earth  in  its  revolution  about  the  sun  not  only 
continues  its  journey  by  reason  of  the  action  of  some  initial 
force  long  since  spent,  but  at  a  rate  which  makes  the  years 
as  periods  of  its  revolution  of  a  uniform  length,  argues  that 
with  its  enveloping  atmosphere  the  earth  sweeps  through 
spaces  destitute  of  any  matter,  even  of  the  most  rarefied  gase- 
ous nature,  and  so  meets  no  resistance  to  its  motion. 

When  a  body  is  acted  upon  in  any  such  way  as  to  cause  a 
change  in  its  form  without  a  change  in  its  position,  it  is  said 
to  be  under  a  strain.  The  body  is  more  or  less  deformed. 
The  force  causing  a  strain,  whatever  the  force  may  be,  is 
called  a  stress.  The  two  terms  are  correlative,  i.e.,  the  use 
of  one  of  them  implies  the  other. 

The  properties  denned  above  are  characteristics  of  all 
matter  whether  in  solid,  liquid,  or  gaseous  state.  They  are 
the  so-called  general  properties.  There  are  also  specific 
properties  of  matter  characterizing  certain  bodies  only. 


MATTER  AND  FORCE  155 

These  are  dependent  upon  molecular  forces  acting  within 
the  body,  and  are  attributes  more  especially  of  solids.  Of 
these  only  the  following  are  defined: 

Tenacity  refers  to  that  property  manifested  by  a  body  in  the  resistance 
it  offers  to  being  pulled,  bent,  or  twisted  apart.  A  dry  dead  twig  may 
easily  be  broken,  but  the  toughness  of  the  fibres  of  flax  and  of  other  tex- 
tiles makes  possible  their  incalculable  value  to  mankind  in  fabrics  and 
cordage. 

Elasticity  manifests  itself  in  a  tendency  in  bodies  when  released  from  a 
strain  to  return  to  an  original  form  or  volume.  Bodies  may  be  flexible  or 
compressible,  they  may  be  pulled  or  twisted  into  new  forms,  but  it  is  in 
the  tendency  to  recover  from  any  such  strain  that  their  elasticity  is  mani- 
fest. Bodies  such  as  wet  clay  which  may  be  shaped  into  desired  forms 
that  are  retained  by  reason  of  lack  of  elasticity  in  them  are  said  to  be 
plastic, 

When  a  body  falls  we  " explain"  it  by  saying  that  it  is 
caused  by  the  attractive  force  of  the  earth  known  as  gravity. 
This  pull  of  the  earth  is  exerted  not  only  upon  bodies  at  or 
near  its  surface  but  it  reaches  outward  through  all  space, 
attracting  all  other  bodies  in  the  universe.  Sir  Isaac  Newton 
(1642-1727)  formulated  the  belief  now  accepted  as  statement 
of  a  great  general  truth  that  every  particle  of  matter  in  the 
universe  attracts  every  other  particle  in  the  same  manner  as 
the  falling  body  is  attracted  by  the  earth.  This  universal 
pull  of  bodies  upon  one  another  is  called  the  force  of  gravita- 
tion. Little  more  is  known  about  it  than  in  Newton's  day, 
and  what  causes  it  no  one  knows.  When  the  attraction  is 
between  the  earth  and  bodies  at  or  near  its  surface,  the 
term  gravity  is  more  commonly  employed.  The  molecular 
forces  of  cohesion  and  adhesion,  acting  between  the  particles 
of  bodies  at  insensibly  small  distances,  are  likewise  attrac- 
tive forces  binding  matter  together  into  masses.  Gravitation 
acts,  however,  through  measurable  (sensible)  distances  and 
throughout  the  extent  of  the  universe. 

It  was  part  of  Newton's  statement  ("law")  concerning 
gravitation  that  its  value  was  affected  both  by  the  masses  of 


156  GENERAL  SCIENCE 

the  bodies  involved,  and  by  their  distances  apart.  With  the 
mass  of  the  earth  considered  constant,  and  the  value  of  its 
attraction  directly  proportional  to  the  amount  of  matter  in 
the  body  attracted,  it  becomes  easily  possible  by  means  of  the 
spring  balance  to  determine  the  relative  pull  of  the  earth 
for  different  bodies.  The  weight  of  a  body  is  the  value  of  the 
earth's  attraction  for  it.  Weighing  it  is  finding  out  how 
many  times  greater  this  attraction  is  than  that  for  some  other 
body  whose  mass  is  taken  as  a  unit.  The  close  association 
of  our  ideas  of  matter  and  of  force  is  noted  in  the  fact  that 
the  name  pound  is  in  use  both  for  the  standard  unit  of  mass 
carefully  safe-guarded  at  Washington,  D.  C.,  and  for  the 


FIG.  53. — -Weighing  is  a  comparison  of  earth  pulls. 

value  of  the  earth-pull  upon  this  mass,  or  any  duplicate  of  it, 
anywhere  in  the  world.  A  like  confusion  exists  in  the  use 
of  the  terms  gram  of  force  and  gram  of  mass. 

One  thing  must  be  noted  in  this  connection,  however, 
marking  a  sharp  distinction  between  a  pound  of  matter  and 
a  pound  of  force.  The  pound  mass  is  an  unchangeable 
quantity  regardless  of  the  place  to  which  it  may  be  taken. 
'On  the  other  hand,  the  earth's  attraction  for  this  pound  mass 
varies  in  value,  and  this  variation  depends  largely  upon 
altitude  (distance  above  or  below  sea-level),  and  upon 
latitude.  This  dependence  upon  latitude  is  due  to  the  fact 


MATTER  AND  FORCE  157 

that  the  earth  is  not  perfectly  spherical,  being  flattened  at 
the  poles.  A  body  taken  towards  the  equator  is  at  the  same 
time  being  taken  farther  from  the  earth's  center.  At  the 
equator  it  is  calculated  that  a  body  is  about  thirteen  miles 
farther  from  the  center  than  when  at  one  of  the  poles. 

The  astronomer  explains  that  gravitation  is  the  great 
controlling  force  by  means  of  which  the  moon  is  made  to 
move  in  a  circular  path  about  the  earth.  All  bodies  when 
moving  tend  to  move  in  straight  lines  by  reason  of  their 
inertia.  It  is  gravitation  that  holds  the  earth  itself  in  a 
circular  path  about  the  sun  as  a  center,  preventing  it  from 
rushing  off  into  space.  The  calculated  value  of  this  pull  of 
the  sun  upon  the  earth  in  order  to  hold  it  to  its  circular 
path  (orbit)  is  a  value  so  great  as  to  pass  comprehension. 
When  a  body  is  whirled  about  the  hand  at  the  end  of  a  string, 
it  is  only  necessary  to  increase  the  mass  of  the  body  and  its 
rate  of  motion  (velocity)  to  overcome  quickly  the  strength  of 
the  string.  So  great  is  the  mass  of  the  earth,  and  so  enor- 
mous is  its  velocity  in  its  orbit  (about  eighteen  miles  per  second}, 
that  any  cable  we  can  conceive  fastening  earth  to  sun  and 
replacing  gravitation  would  be  as  the  strands  of  a  spider's 
web  for  strength. 

SUMMARY 

When  we  say  that  matter  is  anything  that  occupies  space,  it  does 
not  follow  that  we  have  any  considerable  knowledge  of  its  real  nature. 
We  have  merely  named  one  of  the  readiest  ways  of  identifying  matter. 
The  properties  of  matter  are  those  characteristics  by  means  of  which 
bodies  may  be  recognized  and  identified. 

Little  is  known,  too,  of  the  real  nature  of  force,  but  information  is 
available  concerning  the  conditions  under  which  it  becomes  manifest. 

Force  is  the  cause  of  all  changes  occurring  in  matter.  The  different 
ways  in  which  force  manifests  itself,  and  the  difference  in  conditions 
for  its  manifestation,  give  rise  to  a  long  list  of  so-called  forces,  such  as 
heat,  light,  magnetism,  electricity,  gravity,  cohesion,  etc. 

We  have  been  familiar  from  childhood  with  the  effects  of  the  force 


158  GENERAL  SCIENCE 

of  gravity.  The  pull  of  the  earth  gives  weight  to  bodies,  and  causes 
the  familiar  phenomenon  of  falling  bodies.  There  is  sufficient  reason 
for  believing  that  every  particle  of  matter,  regardless  of  where  it  may 
be,  exerts  a  pull  upon  all  other  matter  everywhere.  Why  it  does  this 
is  unknown.  The  value  of  the  force  of  gravitation  depends  upon  the 
amount  of  matter  in  the  bodies  attracting  each  other,  and  upon  the 
distances  separating  them. 


FIG.  54. — Alighting  from  a  street  car.     When  facing  forward  one  is  less 
likely  to  be  thrown  if  the  car  suddenly  starts. 

A  similar  attraction  exists  between  the  minute  particles  known  as 
molecules  of  which  matter  is  supposed  to  be  made  up.  The  distance 
through  which  this  molecular  force  is  exerted,  however,  is  too  small  for 
any  actual  measurement. 

Exercises 

1.  Distinguish  between  mass  and  density  of  bodies. 

2.  What  is  meant  by  the  properties  of  bodies? 

3.  Name  four  forms  of  strain.     Of  these,  which  are  involved  in  testing  the 
tenacity  of  a  piece  of  wire? 

4.  When  mercury  is  spilled  and  breaks  up  into  globules,  why  do  they  retain  a 
spherical  form  as  they  roll  about? 

6.  What  is  meant  by  the  ductility  of  metals?     Mention  several  uses  of  iron 
when  in  the  form  of  wires. 


MATTER  AND  FORCE  159 

6.  What  property  of  matter  is  involved  where  one  is  thrown  when  stepping 
off  a   moving  car?     Why  should   one  face   toward   the   front  end  of  a 
street  car  in  alighting  from  it? 

7.  Is  the  earth's  pull  upon  a  person  (his  weight)  affected  by  having  another 
'   body  come  in  between  him  and  the  earth?     Is  there  any  way  in  which 

to  screen  a  person  from  the  pull  of  the  earth,  i.e.,  of  preventing  the  force 
of  gravity  from  acting  upon  him?  What  then  is  true  of  a  person  when 
he  is  "losing  weight"? 

8.  What  is  a  pound  (a)  of  force;  (b)  of  matter? 


VIII.  WORK  AND  MACHINES 

MEANING  OF  THE  TERMS  WORK  AND  ENERGY 

When  a  magnet  picks  up  bits  of  iron,  when  heat  causes 
water  particles  to  separate  into  steam  as  in  the  locomotive, 
when  the  force  of  gravity  causes  the  falling  of  bodies,  just  as 
when  muscular  force  moves  a  book  from  one  position  to 
another,  work  is  done.  And  when  work  is  done  by  causing 
motion  in  matter,  energy  has  been  used  in  doing  the  work. 

All  changes  in  matter — changes  in  size,  temperature, 
state,  form,  position — are  the  results  of  the  action  of  forces. 
But  when  it  is  desired  to  lay  emphasis  upon  changes  in  posi- 
tion, whether  of  the  body  as  a  whole  or  of  the  particles  within 
it  and  of  which  it  is  composed,  " energy"  is  said  to  have  been 
used,  and  "work"  to  have  been  done.  Wherever  work  is 
done  there  is  expenditure  of  energy,  and  the  amount  of  one  is 
a  measure  of  the  other. 

It  is  an  accepted  belief  or  "theory"  held  by  scientists  that 
there  is  no  such  thing  as  the  destruction  of  energy,  and  that  it 
is  impossible  to  create  energy.  It  should  be  remembered  in 
this  connection  that  the  theories  of  science  are  based  upon 
what  is  known  to  be  true,  and  that  likewise  they  are  in  accord 
with  known  facts  insofar  as  their  verification  is  possible. 
Theories  are  thus  more  than  mere  opinions. 

The  utmost  that  man  can  do  is  either  to  transfer  energy 
from  one  body  to  another,  or  to  transform  one  kind  of  energy 
into  some  other  kind  as  when  electrical  energy  is  converted 
into  heat  and  light  energy.  In  all  such  transformations  and 
transferences  there  is  waste  in  the  amount  of  energy  available 
for  man's  use,  often  a  large  waste,  but  it  is  believed  that  there 

.160 


WORK  AND  MACHINES  161 

is  no  destruction  of  energy.  When  energy  is  expended 
upon  bodies  without  causing  any  apparent  motion  in  them, 
or  not  enough  motion  to  account  for  all  the  energy  ex- 
pended, these  bodies  become  heated,  i.e.,  molecular  motion 
in  them  is  increased  and  their  temperature  rises. 

Rubbing  a  match  head  on  a  rough  surface  raises  its  tem- 
perature sufficiently  to  cause  ignition.  The  muscular  energy 
expended  is  much  in  excess  of  what  is  needed  to  move  the 
match  through  the  air  from  its  one  position  to  the  other. 
The  excess  energy  that  is  used  in  moving  the  match  over- 
comes the  resistance  to  motion  offered  by  friction.  It 
appears  as  heat,  and  ignition  occurs.  Electricity  in  passing 
through  the  filaments  in  electric  light  bulbs  produces  heat, 
or  molecular  motion,  instead  of  causing  any  motion  from 
place  to  place  in  the  lamp  parts.  When  one  attempts  to 
break  a  piece  of  iron  or  copper  wire  by  bending  it  back 
and  forth  rapidly,  the  wire  may  become  so  hot  as  to  burn  the 
fingers.  Part  of  the  muscular  energy  used  appears  as  heat 
in  the  wire.  A  piece  of  metal  subjected  to  a  vigorous  pound- 
ing becomes  too  hot  to  hold  in  the  hand.  The  use  of  oil 
and  other  lubricants  in  machinery  is  to  lessen  the  waste  of 
mechanical  energy  through  its  conversion  into  heat. 

The  sun  is  considered  the  primary  source  of  the  energy  that 
causes  all  changes  in  the  material  world  about  us.  Upon 
this  solar  energy  all  life  upon  the  earth  is  dependent.  It  is  a 
matter  of  great  interest  to  learn  by  readings  in  Astronomy 
how  scientists  account  for  the  tremendous  annual  output  of 
energy  from  the  sun,  and  what  beliefs  are  entertained  as  to 
the  period  through  which  this  may  continue.  Some  of  the 
ways  in  which  plant  life  appropriates  it,  and  how  in  turn 
it  becomes  available  for  animal  life,  will  be  discussed  later. 
(Pages  226  and  268.) 

To  account  for  the  transmission  of  this  energy  from  the 
sun  to  the  earth  it  is  necessary  to  believe  in  the  existence  of  a 


id2  GENERAL  SCIENCE 

means  for  its  transmission.  There  must  be  a  medium  by 
which  it  can  pass  through  that  vast  extent  of  space  between 
earth  and  sun  which  is  supposed  to  be  destitute  of  matter.  It 
is  quite  impossible  to  conceive  energy  transmitted  from  one 
place  to  another  without  a  medium  for  its  transmission.  It 
is  supposed,  and  it  is  just  a  supposition,  that  such  a  medium 
does  exist.  It  is,  however,  wholly  unknown  to  us  through  the 
senses,  and  so  cannot  be  matter.  By  supposing  it  to  exist, 
and  attributing  to  it  certain  properties,  all  phenomena  of 
-the  transmission  through  space  of  heat,  light,  and  electricity 
can  be  accounted  for.  Their  transmission  occurs  just  as  if 
such  a  medium  did  exist,  and  belief  in  its  existence  is  as 
assured  as  though  it  were  a  material  medium  that  could  be 
weighed  and  handled.  As  a  belief  this  is  much  the  same  as 
when  we  assert  that  a  person  has  a  mind,  or  that  he  possesses 
the  sense  of  sight,  because  he  acts  just  as  if  such  were  the  case. 
By  making  this  supposition  the  behavior  of  the  individual 
can  be  explained  and  interpreted  in  a  way  wholly  impossible 
otherwise. 

Somewhat  as  sound  waves  are  transmitted  outward  from 
any  source  by  the  air  or  other  material  medium  so  we  may 
conceive  a  succession  of  pulsations  in  the  medium  known 
as  ether.  Whether  these  wave  motions  manifest  themselves 
to  us  as  heat,  light,  or  electricity  depends  upon  their  number 
per  second  reaching  us,  i.e.,  upon  their  wave  frequency.  It  is 
to  be  remembered,  too,  that  not  only  may  bodies  upon  which 
these  ether  waves  fall  absorb  the  motions  and  become 
heated  thereby,  but  these  waves  may  be  reflected,  or  they 
may  be  transmitted  into  the  spaces  beyond. 

SUMMARY 

Work  is  done  when  bodies  are  moved,  and  when  any  change  in 
motion  occurs  in  the  body  as  a  whole  or  in  its  molecules.  Both  the 
work  accomplished  and  the  effort  expended  in  doing  the  work  are 
measured  in  the  same  units  and  theoretically  are  equal  in  amount. 


WORK  AND  MACHINES  163 

However,  there  is  a  difference,  sometimes  a  great  difference,  between 
the  energy  expended  and  the  amount  of  useful  work  done.  The  ratio 
of  useful  work  done  to  the  energy  used  in  doing  it  constitutes  the  effi- 
ciency of  the  machine  employed. 

The  terms  work  and  energy  are  correlative.  The  use  of  one  implies 
the  other.  A  distinction  which  may  be  made  in  use  of  the  terms  force 
and  energy  is  that  while  all  changes  in  matter  are  the  results  of  forces 
acting,  the  term  energy  is  to  be  employed  only  when  it  is  desired  to 
emphasize  the  fact  that  a  change  due  to  any  force  involves  motion  in 
a  body  or  in  its  parts.  Work  has  been  done  upon  the  body. 

While  theories  are  only  suppositions,  they  are  always  based  upon 
facts,  and  in  their  applications  must  always  accord  with  the  facts. 

For  the  transmission  of  energy  from  place  to  place  some  means  or 
medium  is  necessary.  To  account  for  the  transmission  of  solar  energy 
through  space  destitute  of  all  matter  it  is  believed  that  an  ether  medium 
exists.  Only  by  supposing  the  existence  of  such  a  medium  can  the 
transmission  of  light,  heat,  and  other  forms  of  energy  outward  through 
space  be  accounted  for.  Assuming  that  it  does  exist  makes  possible 
an  understanding  of  phenomena  otherwise  inexplicable. 

Exercises 

1.  What  sharp  distinctions  are  made  in  the  use  of  the  correlated  terms  force, 
energy,  and  work? 

2.  What  is  the  literal  meaning  of  the  terms  (a)  transfer;  (b)  transform? 

3.  In  the  realm  of  science  does  believing  a  thing  so  make  it  so?     When  only 
does  supposition  become  worthy  of  being  entertained  as  a  belief  or  an 
opinion? 

4.  Distinguish  between  theory  and  mere  speculation.     Of  what  service  is 
theory  in  the  study  of  any  science? 

5.  What  meaning  has  the  statement  that  only  in  beliefs  well-founded  are 
the  great  achievements  of  men  wrought  out? 

6.  State  the  argument  for  the  existence  of  an  ether  medium. 


LEVERS  AND  PULLEYS 

However  simple  or  however  complicated  any  device  for 
doing  work  may  be  it  is  called  a  machine.  Through  the 
use  of  machines  men  employ  to  advantage  their  own  strength 
as  muscular  force,  and  what  is  of  far  greater  importance 


164 


GENERAL  SCIENCE 


they  are  able  to  make  use  of  the  various  and  exhaustless 
forces  of  nature.  Among  the  simple  machines  employed 
in  a  wide  range  of  usefulness  is  the  pulley  which  is  a  modified 
form  of  a  lever.  Any  full  understanding  of  pulleys  involves  a 
discussion  of  levers. 

When  a  force  (P)  is  employed  to  overcome  a  resistance  or 
lift  a  weight  (W)  by  use  of  a  lever,  it  may  be  considered  that 
the  lever  is  essentially  a  rigid  bar  turning  about  a  pivot  or  an 
axis.  This  point  of  support  is  known 
as  the  fulcrum  (F).  It  is  not  neces- 
sary that  levers  be  straight,  although 
they  are  usually  represented  in  books 
by  straight  lines. 

P  may  be  on  the  side  of  the  fulcrum 
opposite  W  as  in  first  class  levers,  or 
W   may  be   between  F  and  P  as  in 
second  class  levers,  or  P  may  be  be- 
tween F  and  W  as  in  third  class  levers1. 
The  power  arm   (Pa)  may  be  con- 
sidered as  a  radius  of  the  arc  traversed 
by  P    around  F   as   a   centre.     This 
means  that  the  straight  line  represent- 
ing the  actual  length  of  the  power  arm  of  a  bent  lever  may 
be  largely  outside  the  body.     The  weight  arm  (Wa)}  too, 
may  lie  outside  the  lever. 

It  is  worth  while  to  represent  these  three  kinds  of  levers  as 
described,  using  straight  lines  upon  which  lettered  positions 
are  assigned  for  the  effort,  the  resistance,  and  the  fulcrum. 
The  correctness  of  these  constructions  should  then  be  verified 
by  reference  to  drawings  in  some  text  in  Physics. 

In  all  cases  the  movement  of  a  lever  is  one  around  the 

1  Archimedes,  the  Greek  philosopher  (287-212  B.C.)  is  said  to  have  asserted 
that  he  could  lift  (overturn)  the  earth  if  he  but  had  a  place  for  a  fulcrum 
somewhere  out  in  space  off  the  earth's  surface. 


FIG.  55. — A  bent  lever. 
P  F,  Power  arm;  W  F, 
weight  arm. 


WORK  AND  MACHINES  165 

fulcrum  as  a  centre.  The  lever  is  supposed  to  remain  fixed 
so  far  as  motion  from  one  place  to  another  is  concerned. 
No  rotary  motion  occurs  when  the  value  of  the  effort  balances 
that  of  the  resistance,  and  the  lever  then  is  in  a  state  of 
equilibrium.  It  is  wholly  free  to  move,  and  is  acted  upon  by 
forces  capable  of  moving  it,  but  the  effects  of  P  and  W 
are  so  counter-balanced  that  no  motion  occurs. 

The  effect  of  P  is  calculated  by  multiplying  together  the 
value  of  P  and  the  length  of  Pa.  This  product  is  called  the 
moment  of  P,  and  the  use  of  this  term  may  properly  be  con- 
fined to  forces  acting  on  bodies  to  produce  rotary  motion. 
The  moment  of  W  is  calculated  in  a  similar  manner,  and  P 
and  W  are  in  equilibrium  when  their  moments  are  equal 
regardless  of  the  kind  of  lever  employed.  The  term  applies 
equally  well  in  the  use  of  pulleys. 

It  becomes  evident  from  any  such  discussion  of  moments 
that  to  maintain  equilibrium,  or  to  have  the  moment  of  P 
sufficiently  large  to  cause  W  to  be  moved,  it  is  possible  to 
employ  a  small  value  for  P  if  Pa  be  correspondingly  long. 
If  Pa  be  made  shorter  and  shorter  then  P  must  become  larger 
and  larger,  and  will  exceed  the  value  of  W  when  the  power 
arm  is  shorter  than  the  weight  arm  as  in  third  class  levers. 

The  farther  out  from  F  either  P  or  W  is  placed  the  longer 
will  be  the  arc  of  the  circle  described  by  them  in  any  move- 
ment of  the  lever.  The  lengths  of  these  arcs  covered  by  P 
and  W  in  any  one  turn  of  the  lever  bear  the  same  relation 
to  each  other  as  do  the  lengths  of  the  arms.  It  is  thus 
possible  to  state  that  P  times  the  distance  through  which  P 
moves  (Pd)  =  W  times  the  distance  through  which  W  moves 
(Wd). 

As  the  time  taken  for  P  and  W  to  move  through  these 
different  distances  is  the  same  for  both,  it  follows  that  which- 
ever is  the  farther  from  F  and  passes  over  the  longer  arc 
will  move  at  a  correspondingly  greater  velocity.  Thus  it  is 


1 66  GENERAL  SCIENCE 

that  P  X  Pv  (power  velocity)  =  W  X  Wv  (weight  velocity) . 
A  great  many  problems  of  interest  present  themselves 
in  everyday  life  which  involve  the  use  of  levers  and  pulleys 
for  applying  force  advantageously.  In  some  cases  the  over- 
coming of  great  resistance  is  accomplished  with  a  small  effort. 
In  other  cases  a  high  rate  of  speed  in  doing  work  is  secured, 
as  when  the  forearm  is  bent  at  the  elbow.  As  result  of  the 
contraction  of  the  muscles  of  the  upper  arm,  a  rapid  move- 
ment of  the  hand  and  of  whatever  it  may  grasp  results. 

The  relationship  then  of  P,  W,  and 
F  is  that  of  a  third  class  lever. 

The  term  momentum  as  used  in 
Physics  has  to  do  with  motion 
also.  But  in  this  case  the  product 
that  is  known  as  the  momentum 
of  the  body  involves  a  motion  of 
translation,  i.e.,  a  change  from 
one  position  to  another  rather 
than  a  rotary  motion.  Its  value 
is  calculated  by  multiplying  the 

quantity  of  matter  in  the  body  (its  mass,  or  more  commonly 
its  weight)  by  its  velocity.  Momentum  presupposes  a  body 
in  motion  in  order  to  be  able  to  speak  of  its  velocity. 
Moment  is  a  term  as  applicable  when  a  body  is  in  a  balanced 
state  about  some  centre  as  when  it  is  in  motion,  and  it  in- 
volves the  conditions  for  rotary  motion. 

SUMMARY 

A  machine  is  any  device  for  doing  work,  and  its  purpose  is  the  em- 
ployment of  forces  of  all  kinds  to  the  greatest  advantage.  This  ad- 
vantage may  in  some  cases  be  a  rapidity  with  which  the  work  is  done, 
in  others  the  small  expense  for  the  power  used,  and  in  others  ease  and 
convenience  in  doing  the  work. 

While  animals  may  be  considered  machines,  ordinarily  the  term  is 


WORK  AND  MACHINES  167 

restricted  to  any  more  or  less  complicated  and  lifeless  mechanism 
devised  and  made  by  man. 

By  means  of  machines  man  can  employ  not  only  the  strength  of 
himself  and  of  other  animals  to  advantage,  but  he  harnesses  the  differ- 
ent forms  of  energy  of  inanimate  nature  to  do  his  bidding.  The  force 
of  gravitation  in  the  energy  of  winds  and  of  running  waters,  the  heat 
energy  in  steam,  and  electrical  energy  from  the  dynamo  and  from 
batteries,  are  familiar  sources. 

There  is  always  waste  of  energy  (not  destruction  of  it)  in  the  run- 
ning of  any  machine.  The  larger  this  waste  the  less  efficient  is  the 
machine.  The  efficiency  of  a  machine  is  expressed  by  stating  what 
per  cent  the  useful  work  done  by  the  machine  is  of  the  energy 
expended  in  doing  it. 

A  study  of  the  so-called  simple  machines  such  as  levers,  pulleys, 
and  the  inclined  plane,  aids  in  an  understanding  of  the  mechanism  of 
those  that  are  more  complicated  and  whose  parts  may  be  modified 
almost  beyond  recognition.  The  screw  and  wedge  may  be  considered 
forms  of  the  inclined  plane,  and  the  wheel  and  axle  a  form  of  pulley. 

A  lever  is  free  to  move  only  about  a  fixed  point  as  a  fulcrum,  and 
does  not  travel  from  place  to  place.  In  the  use  of  a  set  of  pulleys,  those 
that  are  known  as  the  movable  pulleys  are  attached  to  the  body  that 
is  being  moved,  and  travel  with  it. 

Disregarding  all  waste  of  energy  in  any  machine,  the  product  of  the 
effort  put  forth  as  a  power  into  the  distance  through  which  it  acts 
equals  the  product  of  the  resistance  overcome  into  the  distance  through 
which  the  resistance  is  offered.  As  commonly  stated,  power  times 
power  distance  equals  weight  times  weight  distance.  This  is  a  "law" 
or  general  statement  concerning  machines. 

Since  the  time  involved  in  the  motion  of  both  the  power  and  the 
weight  is  the  same,  this  law  of  machines  may  likewise  be  stated  as 
power  times  power  velocity  equals  weight  times  weight  velocity. 

Whatever  effort  is  required  to  overcome  resistance  beyond  this  cal- 
culated value  may  be  considered  as  used  in  overcoming  the  resistance  of 
the  machine.  So  far  as  useful  work  is  concerned  it  is  energy  wasted. 

The  term  momentum  is  applied  to  the  product  of  the  mass  (or 
weight)  of  a  body  into  its  velocity.  This  makes  the  term  applicable 
only  in  cases  when  bodies  are  moved  from  place  to  place. 

The  moment  of.  a  force  has  no  reference  to  velocity.  It  is  appli- 
cable in  cases  of  levers  where  the  motion  is  about  a  fixed  point  as  a 
fulcrum.  A  body  is  in  equilibrium  when  the  moment  of  the  effort  ex- 


1 68  GENERAL  SCIENCE 

pended  upon  it  equals  the  moment  of  the  resistance  offered  to  its 
motion. 

In  the  case  of  levers  the  ratio  between  the  distances  through  which 
power  and  weight  move  is  just  the  same  as  that  of  their  lever  arms 
which  are  radii  of  the  arcs  described. 


ELECTROMAGNETS 

So  common  is  the  use  of  electricity  in  modern  life  that  in 
one  form  or  another  its  phenomena  are  familiar  to  all. 
The  uses  of  electricity  are  so  important  that  some  knowledge 
of  its  development  within  recent  years  becomes  necessary. 
It  is  not  complimentary  to  one's  understanding  of  the  times 
in  which  he  lives,  and  of  the  conditions  affecting  the  affairs 
of  his  day,  not  to  possess  this  knowledge.  Because  of  the 
widespread  use  of  electricity,  and  its  ever  growing  importance 
in  the  affairs  of  men,  this  may  be  called  an  "  electrical  age". 

The  scientist  sees  in  the  water-fall  of  some  mountain  stream 
a*  vast  amount  of  stored-up  solar  energy  previously  expended 
on  the  water  in  its  evaporation,  and  in  its  transportation 
to  the  higher  altitudes  where  condensation  took  place. 
The  man  of  affairs  in  the  world  sees  the  possibility  of  con- 
verting into  electrical  energy  the  power  for  doing  work 
possessed  by  this  running  water,  and  of  transferring  this 
energy  over  wires  to  distant  towns  and  cities  where  it  may 
contribute  to  man's  comfort  and  serve  him  in  manifold  ways. 

A  coil  of  wire  of  many  turns,  and  whose  ends  are  joined 
to  make  a  "closed  circuit,"  has  an  electric  " current"  de- 
veloped in  it  when  it  is  made  to  rotate  very  rapidly  within 
the  influence  of  a  powerful  magnet.  The  discovery  of  this 
fact  by  the  English  scientist  Faraday  in  I83I1  was  a  wonder- 
ful step  forward  in  the  mastery  of  man  over  the  forces  of 

1  And  by  Joseph  Henry,  an  American,  at  a  somewhat  earlier  date.  How- 
ever, it  was  about  forty  years  later  before  the  dynamo  became  an  industrial 
reality. 


WORK  AND  MACHINES  169 

nature.  As  a  result  of  the  painstaking  researches  of  scien- 
tists from  the  days  of  Michael  Faraday  down,  and  of  the 
genius  of  many  inventors,  the  dynamo  uses  solar  energy 
stored  in  the  water-fall,  or  in  the  coal  that  was  formed  long 
ages  ago,  and  places  at  man's  disposal  in  the  most  convenient 
form  an  increase  in  power  for  doing  the  work  of  the  world 
that  is  amazing.  Through  the  study  of  Physics  one's 
knowledge  of  electricity  which  otherwise  might  be  more  or 
less  fragmentary,  becomes  more  comprehensive  and  better 
organized.  This  grouping  and  organizing  of  knowledge 
characterizes  the  study  of  science. 

As  a  machine  the  dynamo  cannot  create  any  energy. 
It  can  only  return  in  the  form  of  electricity  a  portion  of  the 
energy  used  in  its  operation.  The  fact  that  it  does  yield  as 
a  product  a  very  large  per  cent  (90  per  cent  and  upwards) 
of  what  is  transformed  makes  the  dynamo  highly  efficient  as 
a  machine.  The  steam  engine  on  the  other  hand  is  highly 
wasteful  of  the  heat  energy  it  consumes,  its  efficiency  often 
being  less  than  15  per  cent.  Essentially  the  dynamo  consists 
of  a  number  of  closed  circuits  each  having  many  turns  of  wire 
that  is  very  carefully  insulated.  These  coils  are  made  to 
rotate  at  an  exceedingly  high  rate  of  speed  into  and  out  of  a 
succession  of  powerful  electromagnetic  "fields"  arranged 
around  the  circumference  of  the  rotating  group  of  coils 
(armatures).  So  long  as  these  conditions  are  maintained 
there  exists  within  these  closed  coils  an  electric  pressure. 
Special  devices  have  been  invented  whereby  connection  is 
maintained  between  the  wires  of  these  coils  and  an  outside 
or  external  circuit  so  that  a  continuous  outflow  of  electricity 
from  the  dynamo  when  in  operation  becomes  available  to 
furnish,  light,  power,  and  heat. 

It  is  scarcely  more  than  a  generation  since  schools  were 
giving  much  time  to  teaching  the  phenomena  of  frictional 
electricity  typified  in  the  experiment  where  a  dry  glass  rod 


170 


GENERAL  SCIENCE 


is  rubbed  with  dry  silk.  In  the  apparatus  case  of  the  physics 
room  there  was  likely  to  be  a  static  machine  with  various 
pieces  of  apparatus  to  use  with  the  machine.  Interesting 
as  these  experiments  were,  and  valuable  as  the  instruction 
accompanying  them  may  have  been,  they  receive  far  less 
attention  now. 

The  study  of  the  flow  of  an  electrified  condition  along 
conductors  (wires)  as  current  electricity,  and  the  mainte- 
nance of  this  electrified  condition  by  means  of  cells  and  batter- 
ies of  various  kinds,  is  still  an  important  part  of  courses  in 

high  school  physics.  But  more 
and  more  time  is  being  given  to 
the  study  of  electrical  currents, 
electrical  devices,  and  electrical 
changes  in  those  cases  where  the 
electricity  is  produced  by  dynamos. 
The  problem  of  transmission  of 
electrical  energy  without  wires 
has  been  solved.  But  other  achieve- 
ments and  further  advances  in 
human  knowledge  concerning 
electricity  are  probable.  Even  sluggish  minds  may  well 
be  stimulated  in  efforts  to  master  what  has  already  been 
accomplished  in  order  to  be  prepared  to  comprehend  and 
to  make  use  of  what  is  yet  to  be  learned  and  applied. 

The  production  of  electrical  energy  is  closely  associated 
with  magnetism  in  the  dynamo,  and  with  chemical  changes 
in  cells.  The  existence  of  electricity  in  a  circuit  produces 
magnetic,  chemical,  and  heating  effects.  These  may  be 
seen,  for  example,  in  the  electromagnet,  the  electric  lamp,  and 
in  electroplating.  An  excellent  illustration  is  afforded  in 
these  relationships  of  the  significance  of  the  phrase  "  correla- 
tion of  forces" — such  a  relationship  that  through  the  action 
of  one  force  another  force  manifests  itself. 


FIG.  57. — An  electromagnet. 


WORK  AND  MACHINES 
SUMMARY 


171 


The  close  connection  between  magnetism  and  electricity  is  manifest 
in  the  fact  that  pieces  of  iron  and  steel  are  best  magnetized  by  passing 
a  current  of  electricity  through  a  wire  wound  many  times  around  the 
body  to  be  magnetized.  When  the  steel  is  removed  from  the  coil  of 
wire  it  is  found  permanently  magnetized.  No  manifestation  of  the 
occurrence  of  any  change  has  been  apparent  in  the  process.  A  piece 


FIG.   58. — Wireless  telegraphy. 

of  soft  iron  loses  its  magnetism  when  the  current  ceases,  however 
powerful  as  a  magnet  it  may  have  been  while  the  current  was  passing 
around  it. 

The  employment  of  electromagnets  in  door  bells  and  in  telegraph 
instruments  illustrates  their  usefulness  in  causing  motion  back  and 
forth  through  short  spaces.  The  electrical  impulses  causing  this 
motion  may  originate  at  far  distant  places.  As  the  soft  iron  bar 
(armature)  is  alternately  drawn  to  the  magnet  and  then  released,  its 


172  GENERAL  SCIENCE 

motion  may  not  only  be  used  to  ring  bells  and  give  signals  but  to  open 
and  close  other  electrical  circuits.  This  is  seen  in  the  telegraph  instru- 
ment known  as  the  relay. 

Another  manifestation  of  the  relationship  of  electricity  and  magnet- 
ism is  seen  in  the  production  of  electric  energy  in  coils  of  many  turns 
of  wire  each  made  to  rotate  rapidly  into  and  out  of  the  field  of  a  power- 
ful magnet.  The  dynamo  has  become  one  of  the  most  important  of 
the  machines  employed  in  the  service  of  man,  rivaling  the  steam  engine 
in  the  number  and  importance  of  its  services. 

The  transmission  of  electric  signals  through  distances  of  thousands 
of  miles  without  wires  is  now  an  accomplished  fact.  The  possibility 
of  doing  this  is  apparently  due  to  wave  impulses  in  an  ether  medium. 
The  notable  magnetic  and  electrical  disturbances  occurring  here  on 
the  earth  at  times  of  great  disturbances  in  the  sun  probably  have 
reached  the  earth  by  means  of  an  ether  medium. 

Exercises 

1.  Name  an  advantage  (a)  of  horseshoe  magnets  over  bar  magnets;  (6)  of  elec- 
tromagnets (temporary)  over  permanent  magnets. 

2.  How  is  it  that  a  magnet  can  affect  objects  of  iron  at  a  distance? 

3.  Where  the  relay  is  used  in  telegraph  work,  and  a  short  "local  circuit" 
and  battery  wholly  independent  of  the  main  line  is  employed,  in  which 
line  is  the  key  put  for  sending  out  signals  to  other  stations?     Where  is 
the  sounder  placed  for  making  the  signals  received  audible?     Why  so? 


IX.  SOME  CHEMISTRY  OF  EVERYDAY  LIFE 

A  REVIEW  OF  SOME  CHEMICAL  CHANGES 

Every  substance  has  some  distinguishing  characteristics, 
or  properties,  by  which  it  is  known  as  different  from  all  other 
substances,  and  by  means  of  which  when  once  known  it  may 
always  be  recognized.  Physics  and  Chemistry  are  some- 
times spoken  of  as  " fundamental"  sciences  because  they  are 
so  largely  concerned  with  the  properties  of  bodies  by  means 
of  which  the  bodies  are  identified. 

When  a  chemical  change  occurs  in  a  body  the  properties 
by  which  it  was  before  known  disappear  and  other  properties, 
often  widely  different  ones,  become  manifest.  It  is  in  this 
way  that  a  chemical  change  is  known  to  have  taken  place. 
The  original  substance  has  ceased  to  exist,  and  new  sub- 
stances take  its  place.  The  matter  continues  to  occupy 
space,  however,  and  its  mass  remains  the  same.  The  amount 
of  the  new  material  as  determined  by  weight  is  exactly  the  same 
as  that  from  which  the  new  substances  were  formed.  The 
chemical  properties  of  a  body  may  be  considered  those  that 
are  made  apparent  through  chemical  changes,  while  physical 
properties  involve  no  change  in  the  nature  of  the  substance. 

To  understand  better  chemical  changes  in  matter  it  is 
assumed  to  be  true  that  the  molecules  of  a  body  have  phys- 
ical properties  the  same  as  those  of  the  body  as  a  whole, 
and  that  the  molecules  themselves  are  made  up  of  still  smaller 
particles  called  atoms.  These  atoms  have  their  own  charac- 
teristic weight  values.  Atoms  of  the  same  kind  are  believed 
to  have  the  same  weights,  while  different  kinds  of  atoms  have 

173 


174  GENERAL  SCIENCE 

different  atomic  weights.  When  like  atoms  unite  to  make 
molecules  the  substance  is  known  as  an  element  in  chemistry, 
and  when  the  molecules  of  any  substance  are  made  up  of 
different  kinds  of  atoms  the  substance  is  a  chemical  com- 
pound. The  molecules  of  some  compounds,  small  as  mole- 
cules are  conceived  to  be,  contain  large  numbers  of  atoms 
of  different  kinds.  Other  molecules,  as  in  common  salt 
(sodium  chloride) ,  are  believed  to  contain  but  two  atoms  each. 

Many  chemical  changes  occur  when  a  sufficiently  high 
temperature  is  reached,  as  when  a  little  gun-powder  is  heated. 
In  the  chemical  laboratory  it  is  a  common  practice  to  dis- 
solve substances  and  use  their  solutions  in  bringing  about 
chemical  changes.  In  such  cases  heat  is  often  employed  to 
hasten  and  make  complete  the  changes.  In  the  natural 
world  about  us  heat  and  light  from  the  sun,  and  the  presence 
of  moisture  in  the  soil  and  in  the  air,  are  all  agencies  in  aiding 
chemical  changes. 

In  the  decay  of  organic  matter  the  micro-organisms  known 
as  bacteria  are  active  as  agents  in  the  chemical  changes  that 
occur.  In  the  processes  of  digestion  not  only  is  chemical 
change  in  the  foodstuffs  promoted  by  solution  and  warmth, 
but  the  digestive  secretions  contain  substances  known  as 
enzymes  whose  uses  are  to  bring  about  chemical  changes  in 
the  food  materials.  These  enzymes  seem  to  cause  chemical 
changes  by  reason  of  their  presence,  and  without  themselves 
undergoing  change.  Diastase  (dl'-a-stas)  produced  in  plants, 
ptyalin  (tl'-a-lin)  in  the  saliva,  pepsin  in  the  gastric  juice  of 
the  stomach,  and  pancreatin  are  examples  of  enzymes. 

The  term  metabolism  (me  -tab'-o-lizm)  is  used  to  include  all 
chemical  changes  occurring  in  the  body  whether  for  its 
nourishment  or  for  removal  of  the  waste  due  to  life  activi- 
ties. The  maintenance  of  bodily  conditions  favorable  to 
these  chemical  changes  constitutes  to  a  large  degree  the 
problem  of  health  and  length  of  life.  Impaired  metabolism 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  175 

means  loss  in  efficiency,  even  when  serious  illness  does  not 
occur.  A  physician  in  times  of  illness  seeks  through  right 
hygienic  conditions  and  the  use  of  medicines  to  restore  in 
his  patient  those  bodily  conditions  favorable  for  normal 
chemical  activities.  The  work  done  by  the  cells  of  the  body, 
and  by  its  various  organs,  is  through  chemical  changes 
brought  about  in  them  and  by  them.  One  value  of  exercise 
lies  in  its  direct  stimulation  of  these  chemical  changes, 
and  in  the  maintenance  of  conditions  favorable  to  their 
accomplishment.  Lack  of  wisely  chosen  exercise  results  in 
an  impaired  metabolism,  and  a  decrease  in  bodily  vigor  and 
efficiency. 

Fermentation  as  a  common  chemical  change  may  be  the 
result  of  the  growth  of  yeasts  as  in  bread,  or  of  bacteria  as  in 
the  " mother"  of  vinegar.  In  all  cases  the  action  of  any 
enzyme  or  the  development  of  bacteria  ceases  when  un- 
favorable conditions  arise.  Oftentimes  the  life  activities 
of  the  bacteria  themselves  produce  these  unfavorable  condi- 
tions as  in  the  case  of  the  souring  of  milk  and  of  vinegar. 
When  a  certain  degree  of  acidity  is  reached  the  action  ceases. 
The  acid  in  the  gastric  fluid  of  the  stomach  is  unfavorable  for 
any  continued  action  of  the  ptyalin  of  the  saliva. 

When  the  chemical  element  chlorine  (Cl)  is  liberated  from 
its  compounds  in  the  presence  of  water  (H2O),  so  great  is  the 
attraction,  or  affinity,  of  chlorine  for  hydrogen  that  a  chemical 
change  is  likely  to  occur  between  these  two  elements  to  form 
the  compound  hydrogen  chloride,  or  hydrochloric  acid  (HC1), 
with  the  liberation  of  the  element  oxygen  (O). 

Under  such  conditions  the  free  oxygen  by  reason  of  its 
great  chemical  affinity  is  likely  to  unite  with  whatever  may 
be  at  hand  that  is  readily  oxidized,  thus  " burning  it  up"  and 
completely  changing  its  nature.  Organic  matter  in  solution 
in  drinking  waters  is  likely  to  cause  sickness,  and  disease 
germs  are  sometimes  present  in  water  for  household  uses. 


176  GENERAL  SCIENCE 

Both  may  be  disposed  of  by  treating  the  water  with  small 
amounts  of  substances  that  give  off  chlorine  when  in  water. 
One  such  compound  is  known  as  calcium  hypochlorite,  and 
in  an  impure  form  it  is  sold  in  cans  as  "  bleaching  powder." 
Its  uses  as  a  disinfectant,  for  destroying  offensive  odors  from 
decaying  organic  matter,  and  for  bleaching  cotton  goods, 
all  are  the  result  of  this  oxidizing  process  that  follows  the 
chemical  change  between  the  chlorine  and  water. 

Among  the  items  of  household  supplies  there  are  few  where 
greater  inconvenience  would  be  caused  in  doing"  without 
them  than  in  the  case  of  friction  matches.  People  camping 
out  are  at  times  painfully  aware  of  this.  Yet  it  is  less  than 
a  hundred  years  since  they  have  been  used.  The  heads  of 
safety  matches  consist  of  some  substance  rich  in  oxygen, 
such  as  potassium  chlorate,  mixed  with  antimony  sulphide 
and  glue.  The  surface  on  which  the  safety  match  heads  are 
to  be  rubbed  is  a  mixture  of  glue,  red  phosphorus,  and  some 
material  such  as  powdered  glass  to  largely  increase  the  fric- 
tion. Aside  from  the  danger  of  fire  from  the  accidental 
ignition  of  yellow  phosphorus  when  used  in  matches,  its 
deadly  effects  upon  the  workmen  in  match  factories  are  such 
as  to  condemn  its  use. 

SUMMARY 

Where  chemical  changes  occur  it  is  believed  that  the  quantity  of 
matter  involved  in  the  change  remains  the  same.  However,  the  ap- 
pearance of  entirely  different  characteristics  in  the  matter  after  the 
change  warrants  the  statement  that  new  substances  have  been  formed, 
and  that  the  original  substances  have  wholly  or  in  part  ceased  to  exist. 

Elements  in  chemistry  are  believed  to  be  made  up  of  atoms  of  like 
kind,  while  compounds  contain  unlike  atoms. 

Both  heat  and  solution  are  aids  to  chemical  action,  and  in  many  cases 
are  necessary  to  bring  it  about.  Plants  of  microscopic  size  are  agents 
in  bringing  about  decay  in  dead  organic  matter,  and  in  causing  other 
chemical  changes.  Lifeless  substances  known  as  enzymes  promote 
chemical  changes  in  the  digestion  of  foods  and  elsewhere. 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  177 

Metabolism  has  reference  to  those  chemical  changes  occurring  in 
the  body  concerned  with  its  nourishment,  and  with  the  removal  from 
its  cells  of  all  waste  material. 

THE  CHEMISTRY  OF  CLEANING 

No  matter  how  thoroughly  oil  and  water  may  be  shaken 
together  they  soon  separate.  There  is  less  of  adhesive  force 
between  oil  and  water  than  of  cohesion  between  water  and 
water,  or  between  oil  and  oil.  If,  however,  there  be  shaken 
up  with  them  some  such  substance  as  the  white  of  egg  (albu- 
men), it  is  possible  to  cause  the  oil  to  remain  mixed  with  the 
water.  A  liquid  mixture  containing  suspended  (not  dis- 
solved) oil  or  fat  particles  is  called  an  emulsion.  It  generally 
has  a  milk-like  appearance. 

The  value  of  soap  as  a  cleansing  agent  depends  in  part 
upon  the  fact  that  when  dissolved  in  water  it  serves  to  form 
an  emulsion  with  oily  or  greasy  matter.  The  use  of  soap  is 
commonly  accompanied  by  chemical  changes  of  importance, 
too,  especially  in  the  case  of  laundry  soaps. 

Gasoline  when  applied  to  a  grease  spot  on  clothing  simply 
dissolves  the  grease,  and  the  cloth  may  then  be  freed  of  the 
grease  by  a  thorough  rinsing.  If  a  strip  of  absorbent  cloth 
is  put  underneath,  and  gasoline  is  applied  to  the  spot,  any 
washing  of  the  garment  may  be  unnecessary.  The  garment 
can  be  dried  with  a  hot  flat-iron,  using  a  blotter  or  other 
absorbent  body  under  the  place  where  the  spot  was. 

If  a  strong  ammonia  solution  be  applied  to  a  grease  spot  a 
chemical  union  occurs,  and  the  new  substance  formed  is 
soluble  in  water  and  may  be  washed  out.  If,  however,  the 
cloth  is  allowed  to  dry  without  a  thorough  rinsing,  the  new 
compound  (which  is  of  the  nature  of  a  soap)  undergoes 
change,  and  the  grease  spot  reappears  in  the  cloth  much 
enlarged  by  capillary  action. 

If  instead  of  ammonia  water  a  laundry  soap  is  used,  a 
similar  chemical  change  occurs  between  the  grease  and  a 


178  GENERAL  SCIENCE 

substance  in  the  soap  known  as  an  alkali,  the  amount  of 
which  if  excessive  may  act  destructively  upon  the  skin  and 
possibly  upon  the  fibre  of  the  cloth.  The  soapy  compound 
made  with  the  grease  should  be  removed  by  thorough  rinsing. 

Water  used  for  cleaning  purposes  is  said  to  be  "hard" 
where  it  has  in  solution  compounds  of  calcium  and  of  magne- 
sium commonly  spoken  of  as  "lime."  A  chemical  change  oc- 
curs between  these  compounds  and  the  soap  so  long  as  the  sup- 
ply of  them  in  the  water  lasts,  preventing  any  cleansing  action 
by  the  soap.  One  product  of  such  reaction  (chemicaFchange) 
between  the  soap  and  the  lime  in  the  water  is  the  insoluble 
dirty  scum  that  is  such  an  annoyance  in  the  use  of  hard 
waters.  This  "lime  soap"  becomes  lodged  within  the  fibre 
of  clothing  washed  in  hard  water,  injuring  the  fabric  and 
giving  the  clothing  a  dirty  appearance.  The  hardness  of 
water  may  be  measured  by  its  soap-consuming  power. 

The  waste  of  soap  thus  indicated  has  led  to  a  general  use  of 
washing  powders.  These  essentially  are  strongly  alkaline 
substances  in  powdered  form  that  dissolve  quite  readily  in 
warm  water.  As  a  rule  they  consist  very  largely  of  some 
substance  such  as  sodium  carbonate  (Na2CO3),  commonly 
known  as  "sal-soda"  or  "washing  soda",  which  maybe 
purchased  in  bulk  at  a  few  cents  a  pound.  Great  care  must 
be  exercised  in  the  use  of  all  washing-powders  to  secure  com- 
plete solution  of  them  before  their  use  with  clothing,  and  to  be 
certain  that  the  solution  is  not  so  strong  as  to  injure  the  fabric. 

A  laundry  bluing  in  common  use  is  a  compound  of  iron,  and 
garments  must  be  thoroughly  rinsed  to  free  them  of  all  alkali 
before  using  it.  Otherwise  there  will  be  left  on  the  clothing 
spots  of  iron  rust  (oxide  of  iron)  as  the  result  of  chemical 
changes  in  the  bluing  due  to  the  action  of  the  alkali,  or  blue 
streaks  may  appear  where  soap  was  left  in  the  cloth.  There 
should  be  bluing  enough  left  in  the  cloth  to  destroy  the  slight 
natural  yellow  of  cotton  and  linen  fibre. 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  179 

The  chemical  changes  which  occur  in  the  use  of  sodium 
carbonate  to  soften  waters  containing  in  solution  small 
quantities  of  calcium  suphate  (CaSO^  are  thus  expressed: 

CaS04  (soluble)  +  Na2CO3  (soluble)  =  Na2SO4  (soluble) 
+  CaCOs  (insoluble).  The  sodium  sulphate  which  remains 
in  solution  does  not  interfere  with  the  action  of  the  soap, 
and  the  calcium  carbonate  as  a  finely  divided  white  solid  may 
be  ignored  in  the  further  stages  of  the  washing.  Soap  can 
then  be  used  without  waste.  Magnesium  sulphate  (MgSO«) 
present  in  the  water  is  disposed  of  at  the  same  time,  magne- 
sium carbonate  (MgCO  3)  being  precipitated.  Any  carbonates 
of  calcium  and  magnesium  in  the  water  at  first  are  precipi- 
tated as  the  water  is  heated.  Hardness,  due  to  these  carbon- 
ates is  said  to  be  temporary,  while  that  from  the  presence  of 
the  sulphates  of  calcium  and  magnesium  is  said  to  be  perma- 
nent. In  laundries  where  thousands  of  gallons  of  water  are 
used  daily  extensive  plants  for  softening  the  water  are 
installed  at  large  outlays. 

SUMMARY 

In  an  emulsion  of  oil  or  fat  the  finely  divided  particles  are  held  in 
a  suspended  rather  than  a  dissolved  state.  The  milk-like  appearance 
of  the  liquid  is  due  to  the  diffusion  of  light  from  the  suspended  particles 
just  as  fog,  and  the  steam  escaping  from  locomotives,  commonly 
appear  white  by  reason  of  diffusion  of  light  from  the  minute  water 
particles  composing  them. 

The  cleansing  power  of  water  in  laundry  uses  necessitates  the  freeing 
of  all  adhering  dirt  and  greasy  matter  from  the  fabric.  This  is  accom- 
plished by  both  mechanical  and  chemical  means.  In  both  cases  there 
must  be  the  least  possible  injury  to  the  fabric  itself. 

The  carbonates  and  the  sulphates  of  calcium  and  magnesium  are 
soluble  to  some  small  extent  in  water,  and  constitute  the  "lime"  in 
water.  The  carbonates  largely  separate  out  when  the  water  is  heated. 
They  are  said  to  make  the  water  temporarily  hard.  The  sulphates 
must  be  gotten  rid  of  by  chemical  means. 


I8o  GENERAL  SCIENCE 

The  hardness  of  water  is  sometimes  calculated  from  the  amount  of 
soap  consumed  in  ridding  a  measured  amount  of  water  of  its  lime  by 
chemical  action.  This  is  considered  accomplished  when  lather  from 
the  soap  remains  for  some  time  after  it  has  been  formed. 

Exercises 

1.  Explain  the  use  of  borax  in  toilet  and  bath  waters. 

2.  When  only  will  soap  added  to  dish-water  or  wash- water  give  a  suds?    How 
determine  in  either  case  when  enough  washing  powder  has  been  added 
before  making  free  use  of  soap? 

3.  Why  use  bluing  in  the  rinse  water  only  in  laundry  work,  and  never  in  the 
wash  water? 

4.  Account  for  any  lessened  wearing  qualities  in  garments  by  reason  of  fre- 
quent laundering. 

6.  How  proceed  to  rid  a  garment  of  a  grease  spot  by  use  of  gasoline  without 

leaving  the  spot  much  enlarged?     What  is  meant  by  "dry  cleaning"? 
6.  Explain  the  cleansing  power  of  soap. 

ACIDS,  BASES,  AND  SALTS 

Any  accurate  use  of  the  terms  acid,  base,  and  sail  requires  a 
more  extended  knowledge  of  Chemistry  than  can  be  taught 
in  the  study  of  General  Science.  Their  very  common  use 
in  general  science  readings,  however,  almost  necessitates 
some  knowledge  of  the  distinctions  to  be  observed  in  their 
use,  and  something  of  what  these  terms  imply.  The  use 
of  litmus  paper  is  only  an  aid  in  testing  for  acids  and  bases, 
indicating  as  it  does  acid,  alkaline,  or  neutral  effects.  Some 
salts  show  acid  effects  on  litmus  paper,  and  others  turn  red 
litmus  paper  blue,  i.e.,  they  are  alkaline. 

Vinegar  contains  from  3  to  4  per  cent  of  acetic  acid, 
and  sour  milk  has  in  it  lactic  acid;  the  juices  of  oranges, 
lemons,  and  grape  fruit  have  citric  acid;  rhubarb  and  grapes 
have  tartaric  acid1.  But  there  are  acids  lacking  any  sour 

1  In  the  gastric  juice  of  the  stomach  there  is  a  small  amount  of  free  hydro- 
chloric acid  whose  presence  neutralizes  the  alkaline  saliva,  and  tends  to  prevent 
fermentation  of  food  in  the  stomach  by  its  destructive  effect  on  bacteria. 
The  digestive  ferment  pepsin  requires  the  presence  of  an  acid,  too,  for  its 
action. 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  181 

taste,  even  as  there  are  bases  without  the  characteristic 
effects  of  ammonia  and  lime  water  on  litmus  paper.  The 
chemist  resorts  to  other  means  of  classification  than  taste, 
or  effect  on  litmus,  to  establish  the  distinctions  between 
these  important  classes  of  chemical  compounds. 

To  aid  in  making  somewhat  clear  the  distinctions  that 
are  fundamental  in  this  classification,  let  us  make  use  of  the 
formula  employed  by  chemists  to  express  what  is  known  of 
the  chemical  composition  of  some  of  the  substances  listed 
as  acids,  bases,  and  salts.  Only  a  few  of  these  can  be  given 
here.  Through  the  use  of  formulae  the  chemist  employs 
a  short-hand  expression  of  his  knowledge  of  the  composition 
of  substances,  naming  the  chemical  elements  that  enter  into 
their  composition.  He  likewise  reads  into  a  chemical  formula 
the  weight  proportions  of  the  elements,  and  many  other 
facts  that  are  not  apparent  to  one  who  has  not  studied  Chem- 
istry. It  is  possible  to  tell  from  the  formula  whether  a 
substance  is  an  acid,  a  base,  or  a  salt. 

In  the  formulae  of  the  chemical  compounds  given  below, 
note  what  is  common  in  those  (a)  of  the  acids;  (6)  of  the 
bases;  (c)  of  the  salts1. 

Acids  Bases  Salts 

hydrochloric,  HC1  sodium  hydroxide,  NaOH       sodium  chloride,  NaCl 

nitric,  HNO3  potassium  hydroxide,  KOH     potassium  nitrate,  KNO3 

sulphuric,  H2SO4  calcium  hydroxide,  Ca(OH)2  calcium  sulphate,  CaSO4 

hydrosulphuric,  H^S  copper  hydroxide,  Cu(OH)2    copper  sulphide,  CuS 

The  chemist  makes  large  use  of  the  theory  that  when  any 
one  of  these  substances  is  put  into  water  some  of  its  mole- 
cules break  up.  This  dissociation  fo  molecules  always 
yields  two  parts,  and  each  consists  of  an  atom  or  a  group  of  atoms 
that  is  electrified.  One  of  these  electrified  parts  of  a  mole- 
cule (an  ion)  has  electricity  of  one  kind  (positive),  and  the 

1  It  is  to  be  remembered  that  all  these  are  used  as  illustrations  only,  and 
that  any  complete  discussion  of  this  topic  belongs  in  Chemistry. 


1 82  GENERAL  SCIENCE 

other  part  has  the  opposite  kind  of  charge  (negative).  When 
these  ions  reunite,  this  electrification  disappears,  the  one 
kind  neutralizing  the  other.  A  substance  which  thus  breaks 
up  into  ions  is  called  an  electrolyte. 

He  explains  that  the  acid' effect  of  liquids  on  litmus  paper 
is  due  to  the  existence  of  free  hydrogen  (H)  ions,  and  the 
basic  effect  is  due  to  free  hydroxyl  (OH)  ions.  The  neutrali- 
zation of  an  acid  by  a  base  then  becomes  simply  a  chemical 
union  of  these  ions  to  form  H2O  (water),  and  the  withdrawal 
from  solution  of  both  acid  and  basic  ions. 

Such  conceptions  as  these  make  possible  an  understanding 
of  chemical  changes  otherwise  unsatisfactorily  explained. 

It  must  be  noted,  too,  that  the  salt  whose  formula  is  given 
in  every  one  of  the  cases  exhibits  in  its  formula  a  relation- 
ship to  both  the  acid  and  the  base.  A  salt  in  chemistry  is 
defined  as  a  compound  considered  as  having  been  formed  in 
the  reaction  between  an  acid  and  a  base.  These  changes 
as  they  are  supposed  to  occur  may  be  expressed  in  the  form 
of  equations.  The  formulae  before  the  sign  of  equality  rep- 
resent the  substances  that  as  factors  enter  into  the  chemical 
change;  those  after  it  represent  the  substances  that  are 
products  of  the  change.  While  these  equations  are  often 
employed  to  express  what  we  think  may  happen,  it  is  to  be 
remembered  that  their  use  by  the  chemist  is  supposed  to 
express  what  is  known  to  have  happened. 

It  will  be  noted  in  the  formulas  of  all  salts  that  the  hydro- 
gen of  the  acid  has  been  replaced  by  atoms  of  the  metallic 
element  of  the  base.  This  illustrates  one  of  the  best  of  defini- 
tions of  acids,  i.e.,  a  substance  whose  molecules  contain 
hydrogen  atoms  that  are  replaceable  by  a  metal.  A  base 
appears  to  be  a  substance  whose  molecules  consist  of  metallic 
atoms  combined  with  the  hydroxyl  group  (hydroxyl  radical). 
These  definitions  will  come  to  have  a  much  greater  sig- 
nificance with  a  better  knowledge  of  Chemistry.  The  term 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  183 

radical  applies  to  any  group  of  atoms  such  as  OH  which  in 
chemical  changes  appears  to  behave  as  a  single  atom, 
changing  from  molecule  to  molecule  of  different  substances 
apparently  as  a  group  rather  than  as  separated  atoms. 

When  the  formula  for  any  salt  is  given,  it  is  possible  to  find 
the  formula  for  the  acid  from  which  it  may  be  considered  the 
the  salt  was  formed.  This  can  be  done  by  replacing  the 
metallic  atoms  of  the  salt  by  a  number  of  hydrogen  atoms 
chemically  equivalent  to  them.  The  number  of  hydrogen 
atoms  replaceable  by  a  single  atom  of  another  element  meas- 
ures the  valency  of  that  atom.  Thus  the  valency  of  sodium 
in  NaCl  (formed  from  HC1)  is  one,  and  of  copper  in  CuS 
(formed  from  H2S)  is  two.  The  valency  of  an  atom  or 
radical  is  likewise  determined  by  the  number  of  hydrogen 
atoms  with  which  it  will  unite.  Thus  the  valency  of  Cl  in 
HC1  is  one,  and  that  of  the  radical  SC>4  in  H2S04  is  two. 

In  the  study  of  Chemistry  one  must  become  able  to  deter- 
mine the  valency  of  elements  in  compounds.  As  formulae 
of  the  simpler  chemical  compounds  are  met  in  this  text 
and  elsewhere  it  is  worth  while  to  notice  what  seems  to  be 
the  valency  of  different  elements  and  of  any  radicals.  For 
example,  it  will  be  noted  that  the  valency  of  Ca  and  of  S 
is  two  in  the  compounds  CuS  and  Ca(OH)2,  and  that  of  the 
radical  OH  is  one. 

SUMMARY 

A  base  is  a  compound  of  hydroxyl  (OH)  and  any  metallic  atom  or 
radical.  An  acid  is  a  compound  containing  hydrogen  atoms  replace- 
able by  metallic  atoms  or  radicals.  A  salt  is  a  chemical  compound 
that  may  be  considered  as  formed  when  any  of  the  hydrogen  of  an 
acid  is  replaced  by  a  metal. 

In  the  break-up  (dissociation)  of  molecules  when  certain  substances 
dissolve,  the  metallic  atom  or  group  of  atoms  is  conceived  to  be  posi- 
tively electrified,  and  the  negatively  electrified  atom  or  group  is  non- 
metallic  in  character.  The  behavior  of  hydrogen  ions  is  the  same  as 
that  of  the  metallic  ions. 


1 84  GENERAL  SCIENCE 

The  chemist  explains  the  acid  effect  of  solutions  upon  litmus  or 
other  test  papers  ("indicators")  as  due  to  the  presence  of  free  hydrogen 
ions,  while  the  alkaline  effect  is  due  to  the  presence  of  free  hydroxyl 
ions. 

The  formula  used  in  place  of  the  name  of  any  chemical  compound 
not  only  is  a  shortened  way  of  writing  its  name,  but  it  also  states  at  a 
glance  what  elements  enter  into  the  compound,  their  grouping,  and 
their  weight  proportions.  All  this  must  be  known  by  the  chemist 
before  the  formula  can  be  written. 

An  equation  sets  forth  what  substances  enter  into  a  chemical  change 
as  factors,  and  what  are  the  products  of  the  change.  The  combined 
weights  of  factors  and  of  products  must  be  equal,  as  must  the  number 
of  atoms  on  the  two  sides  of  the  sign  of  equality. 

Any  use  of  equation  writing  to  express  what  is  thought  to  have 
occurred,  or  what  may  occur  in  a  chemical  change,  is  liable  to  lead  to 
wrong  conclusions.  Its  proper  use  is  to  set  forth  what  is  known  to  have 
occurred.  It  is  a  means  for  stating  facts  that  have  been  verified  by 
exacting  tests. 

The  valency  of  any  atom  or  radical  is  simply  a  number.  It  tells 
how  many  hydrogen  atoms  will  replace  the  atom  or  radical,  or  with 
how  many  hydrogen  atoms  it  will  unite. 

A  radical  is  a  group  of  atoms  which  in  chemical  changes  behaves 
like  a  single  atom. 

ELECTRICITY  AND  CHEMICAL  CHANGES 

In  the  study  of  electricity  from  cells  there  is  reason  to 
believe  that  the  electrified  condition  passing  along  a  circuit 
and  constituting  the  current  is  being  maintained  by  chemical 
changes  occurring  in  these  cells.  It  is  also  assumed  that  this 
outward  passage  of  the  electrified  condition  is  by  way  of  the 
carbon  plate  in  the  dry  cell,  or  copper  plate  in  the  simple  cell. 

Where  the  terminals  of  a  broken  circuit  are  put  down  into 
an  electrolyte,  that  electrode  by  way  of  which  the  current 
enters  the  electrolyte  is  called  the  anode  (way  in),  while  the 
one  from  which  the  current  leaves  the  electrolyte  is  known 
as  the  cathode  (way  out).  When  a  current  sufficiently  strong 
is  passedjthrough  dilute  sulphuric  acid  as  the  electrolyte, 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  185 

gases  appear  at  both  electrodes.  By  collecting  a  sufficient 
amount  of  them  for  testing,  the  gas  at  the  cathode  is  found 
always  to  be  hydrogen,  and  the  gas  at  the  anode  is  always 
oxygen.  These  gases  are  apparently  from  the  decomposition 
of  some  of  the  water  (H2O)  of  the  solution.  The  process  of 
breaking  up  chemical  compounds  by  passing  an  electric 


FIG.  59. — Silver  plating.  The  passage  of  the  electric  current  through  the 
solution  of  a  silver  compound  results  in  the  deposition  of  a  thin  coating  of 
silver  over  the  exposed  surfaces  of  articles  serving  as  the  cathode  (-electrode). 

current  through  their  solutions  is  called  electrolysis  (electrical 
analysis) . 

Instead  of  the  sulphuric  acid  in  dilute  solution  as  electro- 
lyte there  could  be  used  a  solution  of  some  compound  of 
silver.  With  a  current  sufficiently  strong,  silver  as  a  metal  in 
the  pure  state  would  then  be  deposited  on  the  cathode, 
forming  a  thin  even  layer  or  " plate"  over  any  suitable 


1 86  GENERAL  SCIENCE 

object  employed  as  the  cathode.  Extra  thick  deposits 
would  constitute  " double-plate "  or  "  quadruple-plate." 
In  a  similar  manner  nickel  plating  uses  a  solution  of  a  com- 
pound of  nickel  for  the  electrolyte,  and  copper  plating  uses 
a  solution  of  a  copper  compound. 

In  Electricity  as  in  other  science  subjects,  theory  aids  in  an 
understanding  of  phenomena.  By  use  of  theories  students 
can  comprehend  in  a  few  lessons  the  significance  of  phenom- 
ena whose  explanation  is  the  result  of  years  of  patient  re- 
search on  the  part  of  many  scientists.  It  is  to  be  remembered , 
too,  that  the  accepted  theories  of  science  rest  upon  an 
experimental  basis,  and  seem  to  be  verified  in  all  cases  where 
they  are  applicable.  At  the  same  time  they  must  never  be 
considered  as  statements  of  what  is  known  to  be  true  beyond 
question. 

To  aid  in  an  understanding  of  electrolysis  what  is  stated  on 
page  181  under  Acids,  Bases,  and  Salts  is  conceived  to  be 
true.  When  some  substances  are  dissolved,  not  only  are 
their  molecules  separated  and  scattered  throughout  the 
solvent,  but  the  molecules  themselves  break  up  into  two  parts 
each  known  as  ions.  These  parts  may  consist  of  single  atoms 
or  of  groups  of  atoms,  and  the  more  dilute  the  solution  the 
larger  the  extent  to  which  this  dissociation  is  carried.  In 
the  case  of  sulphuric  acid,  the  groups  are  considered  as  H2 
and  S04.  These  electrified  atoms  or  groups  of  atoms  act 
as  carriers  of  electricity  and  serve  to  complete  the  circuit  of 
the  current  used  in  electrolysis. 

In  the  case  of  solutions  of  compounds  of  metals  the  metallic 
ions  pass  from  the  solution  to  the  cathode  where  they  give 
up  their  charge  of  electricity,  and  as  atoms  free  of  electrifica- 
tion they  collect  on  the  cathode  as  pure  metal.  It  is  found 
that  if  the  anode  in  such  cases  consists  of  the  same  kind  of 
metal  as  that  which  is  being  deposited,  or  of  any  impure 
form  of  it,  this  anode  wastes  as  result  of  the  electrolytic 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  187 

action.  The  electrolyte  will  then  remain  at  the  same 
strength  of  solution  all  the  time,  and  the  metal  from  the 
anode  will  gradually  accumulate  at  the  cathode  in  a  pure 
state.  Chemically  pure  metals,  such  as  copper,  are  prepared 
or  " refined"  in  great  quantity  for  the  industries  by  electro- 
lytic action. 

When  the  binding  posts  of  the  piece  of  apparatus  known  as 
a  "simple  cell"  are  connected  by  a  wire,  and  the  two  metal 
strips  as  terminals  of  this  wire  are  put  down  into  the  acid 
solution  of  the  cell  as  an  electrolyte,  the  two  plates  of  the  cell 
may  be  considered  as  electrodes.  This  is  true  of  other  kinds 
of  cells.  The  current  set  up  in  such  a  closed  circuit  is  sup- 
posed to  enter  the  cell  from  the  external  circuit  by  the  zinc 
plate  as  anode,  and  to  leave  the  cell  from  the  copper  plate  as 
cathode. 

It  is  interesting  to  note  that  storage  batteries  such  as  are 
used  in  electric  motor  cars  are  " charged"  by  electrolytic 
action.  Chemical  changes  are  made  upon  the  plates  of  the 
storage  cells  by  the  hydrogen  and  oxygen  set  free  by  the 
passing  current.  During  the  charging  process  these  plates 
are  the  electrodes  of  the  " primary  current."  When  these 
chemical  changes  have  been  completed,  the  storage  battery 
is  "  charged."  The  connections  with  the  primary  circuit 
may  then  be  broken,  and  the  storage  battery  is  now  in  its 
turn  capable  of  sustaining  a  current  to  run  the  car  so  long  as 
a  reversed  chemical  action  continues.  When  the  plates 
have  been  restored  to  their  original  condition  chemically, 
the  storage  battery  must  be  charged  anew.  The  "gassing" 
of  the  storage  cells  at  the  completion  of  the  charging  process 
is  but  the  escape  of  oxygen  and  hydrogen  gases  formed  by 
electrolysis,  and  not  longer  used  in  chemical  changes  on  the 
plates  of  the  cells. 

The  marvelous  changes  that  have  been  wrought  by  the 
application  of  electricity  in  the  industries  is  well  illustrated 


i88 


GENERAL  SCIENCE 


in  the  present-day  production  of  aluminum  metal  by  elec- 
trolysis. Bauxite,  an  ore  of  aluminum,  contains  50  per  cent 
or  more  of  alumina  (A^Os) .  This  is  separated  from  the  other 
material  in  the  ore  by  a  series  of  chemical  changes  relatively 
inexpensive.  Alumina  is  insoluble  in  water,  and  its  melting 
point  is  too  high  for  practical  purposes.  However,  a  mineral 
known  as  cryolite  and  imported  in  large  quantities  from 


FIG.  60. — Manufacture  of  aluminum.  A,  A',  a  lining  of  carbon  which 
serves  as  the  cathode  in  the  electrolytic  action.  B,  melted  cryolite  which 
dissolves  the  oxide  of  aluminum  as  it  is  added  from  time  to  time.  The  tem- 
perature of  the  "bath"  is  kept  so  high  by  the  passage  of  the  electric  current 
that  the  aluminum  metal  as  liberated  collects  in  a  molten  state. 


Greenland  not  only  melts  at  a  relatively  low  temperature, 
but  when  in  a  molten  state  it  readily  dissolves  alumina. 
When  a  powerful  electric  current  is  sent  through  such  a 
solution,  the  alumina  is  decomposed.  Oxygen  is  given  off 
at  the  anode  and  pure  aluminum  metal  at  the  cathode. 
The  heat  developed  in  the  passage  of  the  current  through  the 
electrolyte  keeps  the  material  in  the  bath  molten,  and  the 
aluminum  metal  is  drawn  off  from  time  to  time  in  a  liquid 
form. 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  189 

It  is  a  matter  of  interest  to  note  that  the  process  at  present 
employed  for  the  enormous  output  of  this  metal  is  essentially 
the  same  as  that  invented  by  Charles  M.  Hall1  in  1886. 
The  price  of  aluminum  metal  on  the  market  dropped  from 
four  dollars  per  pound  to  twenty  cents  per  pound  as  soon 
as  the  new  process  could  supply  the  demand. 

Aluminum  ware  and  utensils  are  light,  durable,  and  attract- 
ive. The  density  of  aluminum  is  only  2.7  while  that  of 
iron  is  about  7.8.  The  metal  neither  rusts  nor  corrodes. 
The  tarnish  which  dulls  the  appearance  of  aluminum 
kitchen  ware  should  not  be  scoured  off.  It  is  largely  an 
oxide  of  the  metal,  and  serves  as  a  protective  coating. 
Strong  alkalies,  such  as  soda,  should  not  be  used  in 
aluminum  vessels  except  to  clean  them.  The  metal  is 
acted  upon  chemically  by  alkalies,  especially  in  hot  strong 
solutions.  Aluminum  in  a  powdered  form  when  mixed  with 
oil  serves  as  a  paint  for  iron  surfaces,  giving  them  a  cheerful 
neat  appearance  as  well  as  protecting  them  from  rust. 

SUMMARY 

In  the  production  of  electrical  energy  in  cells  by  chemical  changes, 
the  value  of  the  energy  output  from  a  cell  depends  upon  the  difference 
in  the  degree  of  chemical  change  at  the  two  plates.  To  increase  this 
difference  to  a  maximum  one  of  the  plates  usually  is  so  chosen  that  no 
action  at  all  takes  place  upon  it. 

The  plates  of  a  cell  must  be  immersed,  or  embedded,  in  an  electrolyte 
whose  ions  serve  as  carriers  of  electrical  energy  from  one  plate  across 
to  the  other  thus  closing  the  circuit.  The  separation  of  the  plates  by 
any  considerable  thickness  of  liquid,  or  by  a  porous  wall  such  as  a  cup 
of  earthenware,  hinders  this  action  and  increases  the  internal  resistance 
of  the  cell  to  the  passing  of  a  current. 

Whatever  this  electrical  energy  passing  along  the  wire  may  be,  its 
presence  may  be  detected  by  its  effect  upon  a  suspended  magnetic 
needle  such  as  a  magnetic  compass.  Enough  heat  may  be  developed 

1  Hall  was  then  but  twenty-two  years  of  age,  having  graduated  the  year 
before  from  college.  ^ 


GENERAL  SCIENCE 

in  the  conducting  wire  to  be  noticeable,  too,  and  at  times  the  wire  may 
become  incandescent. 

In  the  process  of  electroplating  we  have  a  good  illustration  of  elec- 
trolysis. When  the  terminals  of  a  broken  circuit  are  immersed  in  the 
plating  solution  as  an  electrolyte,  and  a  current  of  electricity  is  sent 
through  it,  the  positively  charged  metallic  ions  in  the  liquid  pass  to 
the  cathode.  Here,  upon  losing  their  electrification,  they  are  deposited 
as  a  metallic  coating  upon  whatever  serves  as  cathode. 

On  the  other  hand  the  negatively  charged  ions  pass  to  the  anode, 
lose  their  electrification,  and  unite  with  the  anode  when  it  is  of  suitable 
material.  At  other  times  they  unite  with  the  water  surrounding  the 
anode,  and  again  at  other  times  escape  as  gaseous  products  into  the 
atmosphere. 

It  must  be  remembered  that  in  this  theory  of  the  dissociation  of 
electrolytes  in  solution  into  ions  there  is  the  most  satisfactory  explana- 
tion of  what  actually  occurs — a  phenomenon  that  otherwise  remains 
complex  and  not  understood. 


LIMESTONE,  AND  OTHER  CARBONATES 

One  of  the  chief  chemical  industries  is  the  manufacture  of 
sodium  carbonate  from  common  salt  (NaCl).  The  impor- 
tance of  it,  and  of  its  related  and  dependent  industries, 
requires  that  every  well-informed  person  have  some  knowl- 
edge of  it,  at  least  as  much  as  may  be  gained  from  a  high 
school  text  in  Chemistry.  The  extent  of  industries  such  as 
this  is  in  no  small  degree  an  index  of  the  industrial  activities 
of  a  nation. 

In  the  Solvay  process  of  manufacture  saturated  solutions  of 
common  salt  are  treated  with  ammonia  (NH3).  This  with 
water  forms  ammonium  hydroxide  or  "ammonia  water" 
(NH4OH).  Carbon  dioxide  (CO2)  passed  into  the  solution 
may  be  supposed  to  form  carbonic  acid  (H2CO3)  with  the 
water.  As  a  final  result  of  chemical  changes  that  occur, 
sodium  bicarbonate  (HNaCO3)  or  " baking  soda"  separates 
out  as  a  finely  divided  solid.  These  chemical  changes  for 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  191 

sake  of  simplicity  are  represented  as  occurring  in  a  series 
thus: 

(1)  NH3  +  H2O  =  NH4OH 

(2)  C02  +  H20  =  H2C03 

(3)  NH4OH  +  H2CO3  =  H2O  +  H(NH4)CO3,  or  ammo- 
nium bicarbonate 

(4)  H(NH4)CO3  +  NaCl  =  NH4C1,  or  ammonium  chlo- 
ride, which  remains  in  solution  +  HNaCO3,  or  sodium  bicar- 
bonate, which  is  precipitated.     Hundreds  of  tons  of  salt  are 
worked  up  daily  in  making  sodium  bicarbonate  at  the  Solvay 
Works,  Syracuse,  N.  Y. 

Upon  heating  the  sodium  bicarbonate  sufficiently  it  is 
converted  into  sodium  carbonate  (Na2CO3),  the  well-known 
"  washing  soda,"  one  of  the  most  extensively  used  of  alkalies 
in  the  arts  and  industries.  The  nature  of  the  chemical 
change  that  occurs  is  shown  in  the  equation 

2HNaCO3  =  H2O  +  CO2  +  Na2CO3. 

Enormous  quantities  of  sodium  carbonate  are  used  in  glass- 
making,  in  soap-making,  for  washing  powders,  and  in  the 
manufacture  of  the  important  compound  known  as  "caustic 
soda"  or  sodium  hydroxide  (NaOH).  The  wide  range  of 
uses  of  sodium  carbonate  is  due  chiefly  to  the  fact  that  it  is 
a  cheap  and  effective  agent  to  neutralize  acids. 

It  is  to  be  noted  in  this  connection,  too,  that  sulphuric 
acid  occupies  the  same  first  rank  in  industrial  importance 
among  acids  that  sodium  carbonate  does  among  alkalies. 
The  amazing  total  amount  of  this  acid1  used  in  the  United 
States,  England,  and  Germany  is  expressive  of  the  manu- 
facturing and  commercial  enterprise  of  these  nations. 

A  description  of  the  making  of  lime  from  the  rock  known 

1  According  to  the  U.  S.  Census  Report  (1914)  one  hundred  ninety-four 
establishments  reported  the  manufacture  of  over  four  million  tons  of  sulphuric 
acid. 


192 


GENERAL  SCIENCE 


Million  Barre/s 


60 
60 
40 
£0 

/ 

J~~ 

/ 

^ 

/ 

as  limestone,  and  of  the  manner  of  use  of  this  lime  in  building 
operations,  may  be  found  in  Chemistry  texts  and  other 
reference  books.  It  has  much  of  interest  in  itself,  and  its 
discussion  may  well  lead  to  further  readings  on  many  related 
topics.  One  such  topic  is  the  nature  of  concrete  and  of 
cement,  both  of  which  are  used  in  enormous  quantities 

annually  for  construction  pur- 
poses. The  growth  of  the 
cement  industry  in  this 
country  from  42,000  barrels 
in  1880  to  80,000,000  barrels 
in  1912  was  especially  rapid 
from  1900  on,  marking  a 
period  of  intense  industrial 
activity.  It  made  possible 
the  completion  of  great  en- 
gineering enterprises  and 
other  construction  works 
previously  out  of  question.  One  of  the  chief  ends  in  those 
study  of  General  Science  is  arousing  an  interest  in  those 
activities  of  men  that  are  applications  of  science,  and  to 
learn  where  to  go  to  get  information  concerning  them  which 
is  both  definite  and  sufficiently  elementary. 

In  the  abundant  limestone  layers  of  the  earth's  crust  the 
geologist  reads  an  intensely  interesting  chapter  of  the  world's 
history.  In  the  rock  he  finds  the  "fossils"  of  shells.  He 
recalls  that  shells  of  clams,  oysters,  and  other  marine  life 
belonging  to  the  division  of  animals  known  as  the  Mollusks, 
are  all  very  largely  carbonate  of  lime.  So  is  the  material 
of  the  great  reefs  and  islands  built  by  the  little  coral  animals 
out  of  mineral  matter  in  solution  in  sea-water.  The  chalk 
deposits  of  the  southern  English  coast  and  elsewhere  are  of 
the  same  chemical  nature,  and  under  the  magnifying  glass 
these  exhibit  the  remains  of  minute  shells.  The  extensive 


1680    IO90   1900    1910 

FIG.    6 1. — Growth    of     the    cement 
industry  in  the  United  States". 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  193 

deposits  known  as  marl  are  an  admixture  of  clay  and  carbon- 
ate of  lime.  They  all  give  evidences  of  an  origin  in  common 
with  the  material  brought  up  by  dredges  from  the  bottom 
of  the  ocean  and  found  to  be  rich  in  shells. 

It  would  seem  that  carbonate  of  lime  in  solution  in  sea 
water  is  appropriated  by  varied  forms  of  marine  life  in  the 
building  of  shells  as  external  skeletons.  These  shells  more  or 
less  broken  are  in  time  deposited  along  with  other  material 
on  the  ocean  floor.  As  result  of  pressure  from  the  material 


FIG.  62. — Concrete  construction.     (Courtesy  of  the  East  Florida  Railway 
^  Company.) 

accumulating  above,  aided  by  the  cementing  effect  of  mate- 
rial from  the  water,  the  whole  becomes  a  compact  mass  in  the 
course  of  time.  By  reason  of  changes  in  the  earth's  crust 
these  sedimentary  rocks,  more  or  less  distinctly  arranged 
in  layers,  may  become  elevated  from  the  ocean  depths  even 
as  we  now  find  them  as  limestone  strata  of  enormous  extent 
and  of  great  thickness. 

Marble  is  limestone  rock  which  is  somewhat  crystalline, 
and  sufficiently  compact  to  take  and  retain  a  high  polish. 
It  is  valued  highly  for  building  purposes,  and  in  art.  Marble 
varies  greatly  in  color,  grain,  and  durability  by  reason, 
possibly,  of  other  earthy  material  with  which  the  calcium 
carbonate  is  often  mixed,  and  because  of  a  variation  in  the 
13 


194  GENERAL  SCIENCE 

heat  and  pressure  to  which  it  has  been  subjected.  Some  of 
the  marble  quarried  in  Italy  and  Greece  has  been  famed  for 
centuries  in  art  because  of  its  snowy  whiteness.  It  has 
a  texture  well  suited  to  the  chisel  of  the  sculptor. 

Great  caverns  are  not  infrequently  met  in  the  limestone 
strata  of  the  earth's  crust,  with  miles  of  underground  pas- 
sages, and  with  vaulted  chambers  having  huge  masses  of 
stone  in  the  form  of  icicles  hanging  from  the  roof.  Here  on  a 
large  scale,  and  through  long  periods  of  time,  the  solvent 
action  upon  limestone  of  water  containing  carbon  dioxide 
has  been  operative.  The  dissolved  material  has  been  carried 
away  by  underground  streams.  Where  water  containing 
the  "lime"  has  evaporated  in  dripping  from  the  roof,  lime- 
stone has  been  left  in  place  either  as  stalactites  above  or  as 
stalagmites  rising  from  the  floor.  These  may  have  become 
joined  into  an  ever  enlarging  mass  that  serves  as  a  pillar 
to  support  the  roof.  The  Mammoth  Cave  in  Kentucky, 
and  the  Wyandotte  Cave  in  Indiana,  are  notable  examples 
in  the  United  States  of  these  caverns  in  limestone  rock. 

Some  sandstones  wet  with  hydrochloric  acid  effervesce 
freely.  If  acted  upon  sufficiently  long  they  are  reduced  to  a 
mass  of  separated  grains  of  sand  by  reason  of  the  removal 
by  the  acid  of  the  limestone  cement.  Such  sandstone,  as 
well  as  limestone  itself,  when  used  for  building  purposes  is 
likely  to  "weather"  more  or  less.  It  crumbles  enough  to 
become  unsightly  and  a  menace  to  the  strength  of  walls. 

Carbonates  of  copper,  of  iron,  of  zinc,  and  of  other  metals 
are  valuable  ores.  From  them  the  respective  metals  are 
generally  obtained: — 

1.  By  roasting  the  ore  which  changes  it  to  an  oxide  just 
as   limestone   (CaCO3)   when   heated  yields   calcium   oxide 
("quick-lime")  and  carbon  dioxide  as  shown  in  the  equation 
CaCO3  =  CaO  +  CO2. 

2.  By  a  "reduction"  of  these  oxides  of  the  metals  to  a 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  195 

more  or  less  pure  metallic  state  by  heating  them  to  a  high 
temperature  along  with  carbon  (coal,  or  coke)  with  the 
formation  of  the  gases  CC>2  and  CO. 

However,  the  steps  taken  in  extraction  of  the  different 
metals  from  their  ores,  whether  as  carbonates  or  other 
compounds,  vary  widely  owing  to  the  character  of  the  earthy 
material  mixed  with  the  metallic  compound,  the  physical 
condition  of  the  ores,  and  the  relative  expense  of  material 
and  labor  involved  in  the  processes. 

The  term  limestone  is  often  loosely  used  to  include  not 
only  the  sulphate  of  calcium  (OaSO*)  as  well  as  the  carbonate, 
but  the  carbonates  and  sulphates  of  the  element  magnesium 
(MgSC>4,  and  MgCOs).  These  latter  are  sometimes  spoken 
of  as  magnesium  limestone.  The  rock  CaSO^H^O  with 
more  or  less  of  earthy  admixture  is  known  as  gypsum. 
When  relatively  pure  it  can  be  heated  to  drive  off  part  of 
the  water  of  crystallization,  and  then  ground  to  form 
" plaster  of  Paris"  whose  uses  for  making  plaster  casts  and 
stucco  work  are  so  well  known. 

SUMMARY 

In  the  industrial  world  the  varied  uses  of  sodium  carbonate,  and  of 
the  numerous  compounds  prepared  from  it,  make  its  production  in 
enormous  quantities  and  at  a  relatively  low  cost  of  utmost  importance. 
In  the  Solvay  process  of  soda  manufacture,  the  raw  material  is  salt, 
ammonia,  and  carbon  dioxide — all  cheap  materials.  The  chemical 
process  involved  is  relatively  a  simple  one,  and  the  market  price  of 
both  the  carbonate  and  the  bicarbonate  in  large  quantities  is  low. 

When  the  limestone  rock  CaCO3  is  quarried  and  heated  intensely 
hot  in  kilns  (kils),  the  valuable  building  material  known  as  lump  or 
"quick"  lime  (CaO)  is  produced.  This  is ''slaked"  by  the  addition 
of  sufficient  water,  and  the  chemical  change  yields  the  finely  powdered 
white  solid  CaO2H2.  This  when  mixed  with  sand  and  water  makes 
mortar  such  as  used  in  laying  walls  of  brick  and  stone. 

The  calcium  carbonate  of  the  enormous  deposits  of  limestone  rock 
may  be  considered  as  once  having  been  in  solution  in  sea  water.  It 


196  GENERAL  SCIENCE 

was  abstracted  and  built  into  shells  by  animals  in  tjie  ocean.  In  due 
time  these  shells,  mixed  with  more  or  less  of  earthy  sediment  from  the 
waters,  accumulated  at  the  ocean  bottom,  and  became  compact. 
Marble  as  calcium  carbonate  seems  to  have  been  subjected  to  much 
heat  caused,  probably,  by  great  pressure. 

Many  of  the  ores  of  the  metals  are  carbonates,  and  when  these  are 
roasted  in  furnaces,  just  as  when  limestone  is  heated  in  kilns,  great 
quantities  of  carbon  dioxide  gas  pass  off  into  the  air.  Oxides  are  left. 

CaCO3  is  nearly  insoluble  in  water.  If  there  be  CO2  in  the  water, 
forming  with  the  water  carbonic  acid  (H2CO3),  the  solution  occurs 
much  more  freely.  This  is  probably  due  to  a  change  of  the  carbonate 
into  the  bicarbonate  of  calcium  whose  formula  is  H2Ca(CO3)2.  This 
dissolves  much  more  readily  than  the  carbonate. 

THE  CHIEF  AMONG  METALS 

Without  coal  as  a  fuel  the  machinery  of  modern  industrial 
life  would  largely  stand  idle.  It  becomes  equally  apparent 
upon  reflection  that  without  metals  there  would  be  few 
machines  to  operate,  and  these  necessarily  of  the  simplest 
type.  Millions  of  the  world's  workers  are  engaged  in  operat- 
ing machinery  in  mills,  factories,  shops,  and  foundries,  or 
in  occupations  dependent  upon  providing  the  raw  material 
for  this  machinery  and  in  the  transportation  of  its  finished 
products.  Transportation  by  land  and  sea,  the  transaction 
of  business,  the  discharge  of  household  affairs,  and  the  carry- 
ing on  of  agricultural  pursuits  without  the  aid  of  machinery 
would  mean  a  return  to  a  semi-civilized  state. 

Something  of  an  idea  of  the  importance  of  metals  in  every- 
day life  is  gained  through  an  attempt  to  list  the  articles  and 
conveniences  made  impossible  by  a  prohibition  of  the  use  of 
all  metals.  There  would  be  no  steam  or  gas  engines,  no 
steamships  or  steam  and  electric  railways,  no  printing  presses, 
no  telegraph  and  telephone  service,  no  suitable  tools  for  the 
artisan  and  builder,  only  the  rudest  and  most  primitive  of 
implements  for  farming  and  of  conveyances  in  travel,  no 
airplanes  and  auto  trucks,  no  heating  plants  and  plumbing, 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE 


197 


no  utensils  of  metal  in  our  homes,  and  no  builder's  hardware 
such  as  screws  and  nails  and  bolts  for  the  construction  of  our 
houses.  An  index  of  the  industrial  activity,  enlightenment, 
and  advance  of  a  nation  in  civilization,  is  the  extent  of  its 
metal  products.  It  was  the  mineral  resources  of  Alsace- 
Lorraine  wrung  from  a  defeated  France  in  1871  that  has  made 
this  territory  so  valuable  to  Germany,  and  the  coal  and  iron 
mines  of  northern  France  and  of  Belgium  were  an  immediate 
objective  of  Germany's  forces  at  the  outbreak  of  the  World 


COUHTRY 


Production  of  Iron  Ore  m  Million  73/?j 

10  to  JO  40  fO  60 


United  States 
German  Empire 
France, 
Great  Britain 
Sweden 
Aus  trig- Hungary 


FIG.   63. — Iron  ore  mined  in  different  countries  in  1913. 

War  in  1914.  An  enormous  output  in  metals,  together  with 
the  fuel  required  for  their  production  and  for  marketing  them 
as  finished  products,  is  required  for  industrial  and  commercial 
supremacy  in  world  affairs. 

In  its  wide  range  of  usefulness  iron  may  be  counted  chief 
among  the  metals.  In  the  production  of  iron  ores  the  United 
States  leads  the  world,  and  in  1913  it  reached  the  enormous 
total  output  of  sixty-two  millions  of  tons.  Its  chief  iron  ore 
deposits  are  in  the  districts  west  and  south  of  Lake  Superior, 
and  in  northern  Alabama  about  Birmingham. 

Chemically  considered  the  metals  are  elements,  but  they 
commonly  occur  as  compounds  of  definite  chemical  composi- 
tion, usually  as  oxides,  sulphides,  and  carbonates.  These 
compounds  are  mixed  with  rock  and  earthy  materials,  and 


1 98 


GENERAL  SCIENCE 


when  present  in  sufficient  quantity  to  warrant  profitable 
extraction  of  the  metal  the  mixture  is  called  an  ore.  Com- 
pounds of  iron  are  widely  distributed  in  soils  often  giving 
them  a  yellow,  brown,  or  reddish  appearance.  The  charac- 
teristic red  of  brick  and  tile  is  due  to  oxides  of  iron.  Bricks 
made  from  clays  free  of  iron  compounds  are  light  yellow  in 
color. 


MILLION   TONS 
65 


IG7O       1875      IBQO      1865      1390       1895       I9OO      /905       I9IO       1 
FIG.  64. — Production  of  iron  ore  in  the  United  States   1870  to   1914. 


The  sulphides  are  perhaps  the  most  abundant  of  the  iron 
compounds  but  are  nearly  worthless  as  ores  owing  to  the 
difficulty  in  completely  ridding  the  iron  from  them  of  all 
sulphur,  a  small  amount  of  which  makes  the  iron  brittle. 
Coal  mined  in  certain  districts  contains  iron  sulphide,  and 
when  burned  it  gives  off  very  offensive  gases  as  sulphur  com- 
pounds. Iron  disulphide  (FeS2)  as  glittering  yellow  particles 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE 


199 


scattered  through  sand  and  rocks  has  often  been  mistaken 
for  gold,  and  is  frequently  referred  to  as  " fool's  gold." 

The  tonnage  passing  through  the  "Soo"  Canal  connecting 
Lake  Superior  and  Lake  Huron  far  exceeds  that  through  the 
Suez  Canal,  or  any  other  of  the  great  water  ways  of  the 
world.  Much  of  this  traffic  is  ore  from  the  northern  Minne- 


FIG.  65. — A  freight  carrier  on  the  Great  Lakes. 
Chamber  of  Commerce.) 


(Courtesy  of  Duluth 


sota  region  en  route  to  the  blast  furnaces  of  the  lake  ports  of 
Milwaukee,  South  Chicago,  Detroit,  and  Cleveland,  and 
(by  rail)  to  Pittsburgh  one  of  the  world's  greatest  centres  of 
iron  and  steel  manufacture.  Return  cargoes  of  coal  for  the 
upper  lake  region  swells  the  tonnage  volume  of  this  enormous 
lake  traffic. 

The  manufacture  of  iron  and  steel  is  so  vitally  connected 
with  national  life  and  prosperity,  and  a  general  understanding 
of  operations  involved  in  producing  commercial  iron  is  so 
readily  acquired,  that  information  concerning  its  sources  and 


200 


GENERAL  SCIENCE 


FIG.  66. — Cross-section  of  a  blast  or  "  reduction  "  furnace  for  the  making  of 
pig  iron.  A,  Outlet  for  molten  iron;  B,  outlet  for  slag;  C,  C',  inlets  for  hot  air 
blast;  D,  outlet  which  conducts  escaping  gaseous  products  to  ovens  for  heat- 
ing the  "  blast  ";  E,  conveyor  which  feeds  into  the  furnace  coke,  ore,  and  lime- 
stone; F,  floor  to  lower  hopper  which  when  filled  automatically  dumps  itself; 
G,  counter-balance  for  floor  of  upper  hopper. 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  201 

manner  of  preparation  for  market  need  not  wait  upon  a  study 
of  Chemistry. 

Iron  is  obtained  from  its  oxides  by  an  intense  heating  in 
"blast"  furnaces  of  a  mixture  of  ore,  fuel  (usually  coke),  and 
limestone.  A  reduction  of  the  ore  is  accomplished  by  reason 
of  the  chemical  combination  of  oxygen  from  the  iron  com- 
pound with  carbon  and  carbon  monoxide  gas  (CO)  from  the 
fuel  at  the  high  temperatures  maintained  day  and  night  in 
the  furnaces  for  months  at  a  time.  The  supply  of  air  re- 
quired to  furnish  the  oxygen  necessary  for  the  combustion 
of  the  fuel  is  forced  through  pipes  into  the  bottom  of  the 
furnace  as  a  "hot  blast."  This  air  has  been  heated  by  pass- 
ing it  through  ovens  kept  intensely  hot  by  burning  under 
them  gases  conducted  through  great  pipes  leading  out  from 
the  top  of  the  covered  furnace  stack.  A  considerable  part 
of  these  gases  is  CO  the  same  gas  which  forms  a  large  per- 
centage of  illuminating  gases  furnished  for  household  uses. 
Iron  set  free  in  a  liquid  form  in  the  furnace  settles  to  the 
bottom,  and  from  time  to  time  it  is  allowed  to  flow  out  into 
moulds  made  in  a  bed  of  sand,  forming  when  solidified  the 
"pig  iron"  of  commerce.  It  contains  about  5  per  cent 
of  carbon  together  with  small  amounts  of  sulphur,  phos- 
phorus, silicon,  and  other  substances. 

When  remelted  this  iron  can  be  made  to  take  the  form  of 
any  mould  into  which  it  is  run,  and  any  markings  on  the 
sides  of  the  mould.  (See  page  92.)  These  castings  when 
quickly  cooled  are  brittle,  but  when  the  cooling  is  continued 
through  many  hours  the  iron  becomes  more  or  less  malleable. 

Wrought  iron  is  nearly  pure  iron,  and  results  from  burning 
out  of  molten  cast  iron  the  carbon,  sulphur,  phosphorus, 
silicon,  and  other  substances  it  contains.  It  is  tough,  ductile, 
flexible,  and  malleable.  Steel  may  be  made  from  wrought 
iron  by  combining  with  it  a  certain  small  carefully  calculated 
per  cent  of  carbon.1  This  amount  is  varied  somewhat  accord- 


202  GENERAL  SCIENCE 

ing  to  the  uses  to  be  made  of  the  steel,  and  the  qualities 
desired  in  it.  Various  small  proportions  of  nickel  or  of  other 
metals  are  sometimes  combined  in  steel  to  give  it  desired 
properties  fitting  it  for  certain  uses  in  parts  of  machinery 
where  great  powers  of  endurance  are  required,  or  in  the 
armor  of  battle  ships  where  impenetrability  without  brittle- 
ness  is  necessary. 

The  separation  from  the  iron  of  the  earthy  material  of  the 
ore  along  with  the  ash  and  clinkers  from  the  fuel  is  facili- 
tated by  the  use  of  limestone  as  a  "flux. "  In  combination 
with  sand  present  in  the  ore  the  calcium  carbonate  at  the 
high  temperature  of  the  furnace  forms  a  molten  glass-like 
mass  which  floats  as  a  viscid  liquid  above  the  molten  iron, 
and  when  withdrawn  as  "slag"  from  the  furnace  from  time 
to  time  it  carries  with  it  the  refuse  material  of  the  furnace. 
The  alternate  layers  of  fuel,  flux,  and  ore  are  fed  at  frequent 
intervals  in  at  the  top  of  the  furnace  stack  where  they  are 
hoisted  by  machinery  continuously  in  operation  so  long  as 
the  furnace  is  "in  blast." 

The  material  mixed  in  the  furnace  with  the  fuel  and  ore  as 
a  flux  varies  in  chemical  nature  and  in  amount  according  to 
the  earthy  constituents  of  the  ore.  Indeed,  throughout 
the  whole  series  of  operations  from  the  raw  ores  to  the  finished 
metal  product  exact  chemical  knowledge  of  the  material 
used  and  of  the  changes  occurring  in  it  must  be  maintained. 
This  makes  possible  an  output  of  metal  of  any  desired  quality. 
No  "guessing"  at  results  is  permissible  in  the  industries. 
The  exactness  attained  in  quality  of  manufactured  products 
by  reason  of  applied  chemical  knowledge  is  strikingly  seen 
in  the  fact  that  steel  of  any  certain  quality  is  sold  under 
contract  for  delivery  a  year  or  more  later,  and  before  the 
ores  or  the  coal  for  reducing  them  have  been  mined.  The 
makers  of  various  fabrics  contract  for  the  delivery  of  goods 
of  certain  desired  colors  before  the  chemicals  to  be  used  as  dyes 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  203 

have  been  prepared,  or  the  cotton  for  the  cloth  has  been 
grown,  or  the  wool  to  be  used  has  been  clipped  from  the 
backs  of  sheep. 

Iron  when  heated  softens  long  before  it  melts,  and  while 
hot  can  be  drawn  into  wire  or  be  rolled  into  sheets  and  other 
desired  forms.  In  the  big  rolling  mills  steel  rails  for  rail- 
roads, and  the  great  pieces  of  structural  iron  for  bridges  and 
for  the  framework  of  big  office  buildings  in  cities,  are  rapidly 
handled  and  given  the  forms  desired  by  means  of  powerful 
machinery  in  use  there.  The  shaping  of  iron  on  the  anvil 
of  the  blacksmith  when  hot,  and  the  welding  of  iron  whereby 
two  pieces  become  one,  is  made  possible  by  the  fact  that 
iron  softens  without  melting  as  it  is  heated. 

Exposed  to  air  and  moisture  iron  surfaces  become  corroded 
with  "rust"  (iron  oxide).  This  can  be  prevented  by  keep- 
ing the  iron  painted,  or  by  means  of  a  thin  coating  of  some 
metal  not  readily  affected  by  the  atmosphere.  The  "  tin- 
plate"  of  dealers  in  metals  used  for  roofing,  kitchen  utensils, 
and  dairy  articles,  is  sheet  iron  which  has  been  dipped  into 
molten  tin,  a  very  thin  coat  of  which  adheres  to  the  iron. 
The  "galvanized"  iron  ware  is  sheet  iron,  wire,  etc.,  which 
has  been  similarly  dipped  into  molten  zinc  which  forms  a 
protective  coating  on  the  iron. 

By  heating  iron  and  steel  to  certain  temperatures  deter- 
mined by  experiment  and  recognized  by  the  skilled  worker  in 
metals  by  the  color,  and  then  cooled  at  a  rate  and  in  a 
manner  likewise  learned  by  experience,  certain  desired 
degrees  of  hardness,  elasticity,  flexibility,  and  tenacity  may 
be  given  these  metals  in  a  process  known  as  tempering. 
Edged  tools  of  all  kinds,  as  swords,  razors,  knife  blades, 
chisels  and  axes  must  be  made  of  tempered  steel.  The  metal 
must  be  sufficiently  hard  to  hold  an  edge  when  ground,  but 
not  so  brittle  as  to  break  easily  when  hard  objects  are 
cut.  It  must  be  flexible  enough  to  bend  without  breaking, 


204  GENERAL  SCIENCE 

but  so  elastic  as  to  spring  back  at  once  into  the  original  form. 
The  hairsprings  of  watches  are  good  illustrations  of  steel 
painstakingly  tempered,  their  cost  representing  largely  the 
labor  expended  upon  them.  Spring  balances  of  tempered 
metal  are  used  for  weighing,  and  comfort  in  travel  is  made 
greater  by  the  steel  springs  under  the  wagon  or  auto  body 
and  underneath  the  railway  car.  The  character  of  the  work 
of  "The  Village  Blacksmith"  has  materially  changed  during 
the  past  fifty  years,  machine  work  in  metals  having  now 
largely  replaced  hand  labor.  However,  the  increase  in 
dependence  of  mankind  upon  the  use  of  metals  in  that  time 
for  comfort  and  well-being  has  been  little  short  of  marvelous. 
In  extent  of  use,  and  in  the  changes  wrought  by  such  uses 
in  the  affairs  of  men  and  of  the  world  at  large,  iron  and  steel 
rank  chief  among  the  metals. 

SUMMARY 

The  industrial  activity  and  commercial  supremacy  of  an  enlightened 
nation  is  intimately  related  to  its  national  resources  in  metals,  and  in 
coal  supplies  for  the  development  of  these  resources. 

By  reason  of  the  enormous  quantities  of  iron  employed  in  the  arts 
and  industries,  and  because  of  properties  which  adapt  it  to  innumerable 
uses,  iron  ranks  first  among  the  metals  in  usefulness. 

The  metals  are  chemical  elements.  An  ore  is  a  mixture  of  rock  or 
other  earthy  material  with  some  compound  of  a  metal  present  in  suffi- 
cient quantity  to  make  its  extraction  profitable. 

The  "pig  iron"  of  commerce  is  a  product  of  the  "blast"  or  "reduc- 
tion" furnace  where  the  iron  ore  as  an  oxide  gives  up  its  oxygen  to 
combine  with  the  intensely  heated  carbon  of  coke  or  coal. 

Castings  of  iron  and  steel  of  excellent  design  are  possible  by  reason 
of  their  expansion  as  they  solidify.  Metals  very  generally  shrink  in 
volume  as  they  change  from  the  molten  to  the  solid  state.  Gold  and 
silver  coins  have  designs  and  lettering  stamped  upon  their  surfaces 
under  pressure  of  powerful  machinery.  Mixtures  of  various  metals  in 
a  molten  state  and  in  certain  proportions  are  known  as  alloys.  Some 
of  these,  such  as  type-metal  and  various  kinds  of  "bronze",  are  suc- 
cessfully moulded  due  to  their  expansion  when  solidifying. 


SOME  CHEMISTRY  OF  EVERYDAY  LIFE  205 

Steel  in  general  is  iron  containing  somewhat  more  carbon  than 
wrought  iron  but  less  than  cast  iron,  the  per  cent  varying  according 
to  the  uses  to  be  made  of  the  steel  and  the  properties  it  necessarily 
must  have. 

The  "tempering"  of  steel  by  workmen  skilled  in  the  art  through 
experience  consists  primarily  in  securing  a  desired  degree  of  flexibility, 
elasticity,  tenacity,  and  hardness.  These  properties  are  varied  by  the 
extent  and  rate  of  temperature  changes  ta  which  the  metal,  and  the 
cohesive  force  acting  between  its  molecules,  is  subjected. 


X.  AT  OUR  HOMES 

ROOMS  OF  THE  HOUSE,"  THEIR  FURNISHINGS,  AND  THE  COST 

or  LIVING 

A  good  home,  together  with  all  the  comforts  and  influences 
and  associations  that  should  centre  in  it,  is  essential  to  the 
largest  degree  of  happiness  in  life.  However  costly  the 
dwelling  that  shelters  a  family,  it  may  be  anything  but  a 
true  home  by  reason  of  the  manner  of  life  of  the  people  who 
inhabit  it.  On  the  other  hand  the  best  of  human  affections 
and  influences  may  centre  in  the  rudest  of  structures.  Yet 
it  remains  true  that  comfortable  and  well-appointed  dwellings 
constitute  a  large  factor  in  having  good  homes.  To  possess 
a  good  home  and  good  home  surroundings,  though  these  be 
moderate  in  cost,  is  worthy  the  ambition  and  sustained  effort 
of  any  American  citizen,  man  or  woman. 

It  is  the  testimony  of  close  observers  that  people  of  limited 
means  and  scant  resources  are  very  commonly  the  ones  who 
fail  to  get  the  full  worth  from  every  dollar  spent  for  home 
comforts  and  for  family  support.  Lack  of  understanding 
of  what  to  get  as  appointments  for  the  home,  and  of  what 
should  constitute  a  suitable  original  outlay  for  them  and  a 
reasonable  period  of  service  from  them,  results  oftentimes  in 
deplorable  waste  and  unnecessary  deprivation. 

There  is  ample  opportunity  for  the  exercise  of  individual 
tastes  and  preferences  after  standards  have  been  established 
concerning  what  is  desirable  for  the  comforts  and  conveniences 
of  modern  family  life.  These  standards  may  be  upon  any 
scale  desired  for  the  persons  whose  interests  are  to  be  served. 

206 


AT  OUR  HOMES 


207 


Public  schools  are  maintained  to  make  possible  higher  ideals 
and  larger  attainments  to  those  who  avail  themselves  of 
school  advantages..  Discussion  of  whatever  contributes  in 
any  large  degree  to  better  living  has  an  important  place, in 
the  school  curriculum.  Courses  in  Home  Economicsjean 
and  should  give  instruction  in  schools  calculated  to  lessen 
waste  in  American  home  life,  and  to  increase  its  comforts  and 


FIG.  67. — A  modern  farm  kitchen. 

general  welfare.  Here  as  in  other  school  activities  advantage 
should  be  taken  of  the  knowledge  gained  through  home 
experiences.  These,  along  with  the  instruction  given  in 
schools,  may  be  so  organized  as  to  uplift  and  improve  life 
in  the  home. 

Wise  expenditure  of  a  family  income,  and  an  efficient 
household  management,  requires  scarcely  less  of  business  and 
administrative  ability  than  does  the  conduct  of  enterprises 
outside  the  home.  Efficiency  counts  not  less  here  than  in 


208  GENERAL  SCIENCE 

the  business  world,  and  to  this  end  both  husband  and  wife 
contribute  in  the  discharge  of  all  duties  assumed  by  them  or 
naturally  devolving  upon  them  as  individuals.  The  arrange- 
ment of  rooms  in  the  house,  and  the  furnishings  that  best 
contribute  to  the  conduct  of  household  affairs,  together 
with  all  matters  connected  with  the  cost  of  living,  are  of 
joint  concern  to  all  members  of  the  family. 

So  great  have  been  the  changes  within  the  last  half  century 
in  conditions  of  family  life,  and  in  the  kind  of  work  necessary 
in  household  affairs,  that  plans  of  houses  built  to-day  differ 
widely  from  those  of  two  generations  ago. 

This  is  true  in  many  respects  other  than  "modern  con- 
veniences". Then  the  kitchen  was  the  centre  of  all  the 
manifold  activities  of  the  home  life.  As  a  veritable  "living 
room"  it  was  made  sufficiently  large  for  use  as  dining  room, 
laundry,  and  sitting  room,  and  for  the  preparation  of  food- 
stuffs for  both  immediate  and  later  family  use.  Nowadays 
it  is  often  a  model  in  its  compact  arrangements  and  con- 
veniences for  work.  It  is  so  planned  as  to  economize  both 
time  and  energy  in  the  discharge  of  the  fewer  household 
duties  that  centre  in  the  kitchen. 

Before  moving  into  any  dwelling  it  is  a  matter  of  wise 
precaution  to  gain  some  knowledge  of  its  history  with  regard 
to  infectious  diseases.  The  possibilities  of  disease  germs 
remaining  lodged  on  its  walls  and  woodwork,  or  in  corners 
and  cracks  where  dirt  has  accumulated,  is  sufficient  reason 
for  care  in  this  respect.  Paint  and  varnish  and  new  wall 
paper  have  values  other  than  for  cleanliness  and  improved 
appearances. 

Since  sunlight  and  fresh  air  are  destructive  of  disease 
germs,  and  dampness  is  conducive  to  their  development, 
all  rooms  in  a  dwelling  should  be  light,  airy,  and  dry.  Win- 
dows are  to  let  in  sunlight  and  air  as  well  as  to  keep  out 
dust  and  cold.  From  time  to  time  the  furnishings  of  rooms 


AT  OUR  HOMES  .  2  09 

should  not  only  be  dusted  out  of  doors,  but  be  exposed  as 
well  to  wind  and  sun.  The  basement  should  be  dry  and 
well  lighted,  and  thoroughly  ventilated.  Its  floors  and  walls 
and  foundations  should  be  so  constructed  as  not  to  harbor 
rats,  mice,  or  vermin  of  any  sort.  The  experiences  of  the 
human  race  long  ago  established  the  fact  that  cleanliness 
in  person  and  in  the  home  not  only  contributes  to  comfort 
and  civilization,  but  is  essential  to  health  and  well-being. 
Boiling  hot  water  for  laundry  uses,  for  washing  dishes,  and 
for  general  household  affairs,  is  a  most  effective  disinfectant, 
and  the  free  use  of  soap  contributes  to  the  same  end. 

Any  consideration  of  the  cost  of  living  naturally  has  much 
to  do  with  food  and  clothing.  Discussions  in  school  of 
food  values  and  prices,  supplementing  home  experiences, 
very  properly  may  emphasize  the  fact  that  there  is  often 
great  waste  in  the  purchase  of  food  supplies  both  in  their 
quality  and  in  the  quantity  secured  for  the  outlay  made. 
The  choice  of  a  wholesome  and  balanced  diet  is  an  important 
topic  of  instruction  in  schools.  Ignorance  in  this  respect 
usually  results  both  in  malnutrition  and  in  thriftless  living. 
The  wide  variation  in  food  values  secured  by  different 
people  in  return  for  the  same  outlay  makes  necessary  some 
elementary  instruction  in  schools  concerning  the  purchase 
and  preparation  of  foods.  It  is  a  matter  of  general  good 
health  and  well-being.  Cheap  cuts  of  meat,  for  instance, 
may  contain  when  properly  cooked  as  much  nourishment 
as  those  more  expensive.  To  substitute  less  expensive 
foods  for  the  more  expensive  ones,  when  the  former  furnish 
just  as  much  food  value,  is  not  only  thrift  but  good  common 
sense.  The  practice  of  doing  without  tea  and  coffee  is 
not  only  a  matter  of  economy,  but  it  has  the  greater  purpose 
of  promoting  health.  Neither  tea  nor  coffee  has  any  food 
value,  and  other  drinks  may  be  provided  that  are  free  from 
the  harmful  effects  of  caffeine. 
14 


2IO 


GENERAL  SCIENCE 


To  choose  habitually  what  really  ministers  in  largest 
.measure  to  one's  welfare  in  matters  of  food,  clothing,  amuse- 
ments, and  self-indulgence  necessitates  a  knowledge  of  the 
experiences  and  teachings  of  others.  This  knowledge  may 
be  gained  at  home  and  at  school,  from  books  and  from  people. 
In  general  it  is  a  reasonable  statement  that  any  girl's  edu- 


FIG.  68. — Canning  as  a  home  occupation. 

cation  is  incomplete  without  some  definite  personal  acquaint- 
ance with  the  affairs  of  a  household,  and  some  degree  of 
proficiency  in  their  management.  And  in  no  less  degree, 
though  in  different  relationships,  every  boy's  education 
should  include  an  intimate  knowledge  of  the  needs  of  a 
household,  and  how  these  can  be  supplied  within  the  limits 
of  a  moderate  income. 

Fortunately  the  cost  of  a  simple  rational  manner  of  living 
is  relatively  low  under  normal  conditions.     It  is  not  only 


AT  OUR  HOMES  211 

relatively  inexpensive  as  a  rule,  but  it  contributes  largely  to 
the  very  best  things  in  life.  To  learn  this  by  experience 
only  may  be  to  repeat  the  mistakes  of  others  rather  than  profit 
by  them.  Thriftlessness  leads  to  poverty  with  all  its  limi- 
tations upon  comfort  and  well-being.  To  become  capable  of 
earning  a  sufficient  income,  and  to  be  intelligent  in  its  ex- 
penditure, usually  involves  long-continued  and  well-directed 
effort  and  much  self-denial. 

Without  the  advantages  of  attendance  upon  school  the 
wage  earner  is  always  at  a  great  disadvantage,  and  the  most 
desirable  positions  of  service,  power,  and  profit  are  often 
unattainable  to  those  lacking  in  education.  The  personal 
characteristics  of  thrift,  industry,  business  integrity,  and 
right  conduct  in  all  things  are,  however,  not  dependent  upon 
schooling.  The  cost  of  right  living  demands  both  a  knowl- 
edge of  what  is  best  for  one,  and  a  willingness  to  do  what  is 
best.  Self-restraint  is  necessary  in  one's  life  to  assure  its 
efficiency,  and  to  avoid  wasting  life's  opportunities  and 
possibilities. 

There  is  always  a  sharp  line  of  distinction  to  be  drawn 
between  outlays  in  life  that  are  necessary  because  of  the 
better  conditions  of  living  that  result  from  them,  and  those 
other  outlays  which  though  desirable  are  not  in  any  sense 
indispensable.  No  community  can  afford  to  be  content  with 
a  contaminated  water  supply  whatever  the  cost  involved 
in  safe-guarding  it.  No  individual  or  family  can  afford  to 
inhabit  a  dwelling  in  the  basement  of  which  water  always 
stands,  whatever  may  be  the  expense  of  drains  and  water- 
proof foundations.  On  the  other  hand  outlays  for  what 
merely  gratifies  expensive  tastes  and  habits  are  always  ques- 
tionable. The  use  of  tobacco  may  very  properly  be  chal- 
lenged on  the  ground  of  its  being  a  useless  expenditure,  as 
well  as  on  the  more  serious  charge  of  its  being  a  menace  to 
the  physical  and  mental  development  of  boys  and  young  men. 


212  GENERAL  SCIENCE 

Generally  speaking  nothing  in  life  costs  too  much  if  there  is 
ample  return  in  well-being  for  the  individual  himself  or  for 
others.  To  attain  the  best  things  in  the  lives  of  individuals 
requires  as  a  rule  long-sustained  efforts  and  sacrifices.  There 
is  doubtful  value  in  any  lesson  that  has  required  no  effort, 
and  in  any  education  or  in  any  fortune  for  which  labor  and 
sacrifice  have  not  been  given. 

There  is  no  other  one  item  in  the  nation's  bill  of  expendi- 
tures so  appalling  in  its  economic  waste  as  that  for  alcoholic 
drink.  Increased  taxation  is  necessary  to  care  for  those 
whose  lives  have  been  wrecked  by  it  directly  and  indirectly. 
The  consumer  gets  nothing  in  exchange  for  his  outlays  that 
ministers  to  his  well-being,  and  it  lessens  his  efficiency  as  a 
worker  and  undermines  his  thrift. 

SUMMARY 

Unwise  expenditures  in  living  expenses  are  a  common  accompaniment 
of  poverty,  and  often  a  direct  cause  for  it.  Lack  of  intelligence  in 
buying  largely  increases  the  cost  of  living  for  those  who  have  abundant 
means;  for  those  of  limited  resources,  it  usually  results  in  getting  far 
less  for  their  outlays  than  they  should. 

Any  proper  valuation  of  articles  purchased  takes  into  account  not 
only  the  original  outlay  for  them  as  cost  price,  but  their  probable 
length  of  service,  and  whether  or  not  they  are  well  suited  for  their 
intended  uses.  This  is  especially  true  in  the  purchase  of  clothing,  and 
when  buying  a  house  and  household  furnishings. 

Business  ability,  and  an  executive  skill  of  high  order,  is  required  for 
an  efficient  household  administration.  In  spending  wisely  the  part 
of  a  family  income  set  aside  for  family  expenses,  the  wife  and  mother 
becomes  as  truly  a  supporter  of  the  family  as  the  husband  and  father. 

Instruction  at  school  in  household  management,  based  upon  home 
experiences  and  applied  to  the  betterment!  of  the  home  life,  constitutes 
an  important  service  rendered  by  the  public  schools.  Public  school 
instruction  in  the  elements  of  home  economics  is  a  means  for  bettering 
individual  welfare  and  improving  social  conditions. 

Health  and  self-respect  alike  demand  that  families  be  well  housed. 
In  congested  centres  of  population  the  high  cost  of  dwelling  places, 


AT  OUR  HOMES  213 

whether  to  own  or  to  rent,  constitutes  an  increasingly  difficult  problem 
in  living.  t 

Ignorance  in  the  choice  of  a  suitable  diet  for  a  family,  and  for  an 
individual,  is  not  only  thriftless  but  it  commonly  results  in  malnutrition, 
ill  health,  and  shortened  lives.  The  well-to-do  are  perhaps  as  often 
victims  of  this  failure  to  regulate  diet  as  are  those  handicapped  by 
poverty. 

Any  rational  manner  of  life  takes  account  of  whatever  ministers  to 
the  comfort,  happiness,  and  welfare  of  individuals  and  of  communities. 
It  seeks  the  highest  efficiency  in  right  living,  and  avoids  whatever  is 
merely  self-indulgence.  A  simple  life  is  quite  consistent  with  a  high 
order  of  living  and  in  a  measure  is  indispensable  to  it. 

It  is  to  be  remembered  that  in  changes  of  styles  in  clothing  there  is 
involved  the  financial  gain  of  those  who  seek  to  market  a  new  stock 
of  goods.  It  is  not  fundamental  to  well-ordered  living  to  discard  cloth- 
ing of  any  sort  while  it  is  yet  suitable  and  serviceable  merely  for  the 
sake  of  changing  to  something  new. 

Exercises 

1.  Who  usually  determines  the  selection  of  things  needed  in  a  household, 
both  as  regards  their  quality  and  the  prices  paid  for  them? 

2.  In  what  sense  is  the  wife  in  a  home,  though  not  a  wage-earner,  as  truly 
a  supporter  of  the  family  as  the  husband? 

3.  Distinguish  between,  (a)  waste  and  thrift;  (ft)  necessities  of  life  and  its 
luxuries;  (c}  comforts  in  living  and  extravagances.     What  factor  very 
largely  determines  in  which  of  these  classes  an  outlay  by  any  person  or 
family  shall  be  put? 

4.  What  advantages  may  there  be  in  cooking  breakfast  cereals  the  day  before 
rather  than  on  the  morning  of  their  use? 

6.  Where  gas  is  used  in  cooking,  or  for  laundry  purposes,  why  is  it  wasteful 
not  to  turn  the  gas  low  as  soon  as  the  wash  water  or  food  begins  to  boil? 

6.  What  precautions  should  be  observed  in  the  purchase  of  fruits  other  than 
securing  honest  measure  and  fair  prices?     What  further  precautions  are 
necessary  before  use  of  these  fruits  as  food? 

7.  Aside  from  a  garden,  name  various  ways  of  reducing  expenditures  for 
foods  without  sacrifice  of  proper  quantity  and  wholesome  quality. 

8.  In  what  ways  is  there  relation  between  the  high  cost  of  living  and  follow- 
ing the  fashions  in  dress? 

9.  To  what  extent  are  "styles"  in  clothing  properly  followed? 

10.  Give  some  arguments  for  the  outlay  involved  in  the  maintenance  (a)  of 
free  public  schools;  (6)  of  churches  as  places  of  public  worship. 

11.  What  is  a  wise  rule  to  follow  in  the  matter  of  outlays  for  amusements? 


214  GENERAL  SCIENCE 

12.  As  an  important  item  in  the  cost  of  living,  what  are  some  of  the  argu- 
ments advanced  to  warrant  a  system  of  insurance  against  fire,  accidents, 
death,  and  disabilities  from  old  age? 

13.  What  may  be  used  to  clean  sinks  and  bath-tubs  of  the  "scum"  from  hard 
water? 

14.  What  is  the  nature  (a)  of  paint;  (6)  of  varnish?     Aside  from  any  improve- 
ment in  appearance,  why  should  woodwork  be  painted  if  it  is  to  be 
exposed  to  the  weather?     Why  have  furniture  and  woodwork  indoors 
varnished? 

15.  What  in  general  should  characterize  the  furnishings  of  a  home? 

16.  State  the  value  of  a  basement  for  a  house  aside  from  the  extra  room  it 
affords. 


FUEL  AND  LIGHTS  FOR  MODERN  HOMES 

Possibly  in  no  one  respect  are  the  comforts  of  modern  life 
more  fully  manifest  than  in  the  heating  and  lighting  of 
American  homes.  Whittier  in  "Snow  Bound"  pictures  for 
us  a  winter's  evening  in  a  New  England  home  of  the  first 
half  of  the  nineteenth  century: 

"Shut  in  from  all  the  world  without, 
We  sat  the  clean-winged  hearth  about, 
Content  to  let  the  north  wind  roar 
In  baffled  rage  at  pane  and  door, 
While  the  red  logs  before  us  beat 
The  frost  line  back  with  tropic  heat; 
And  ever  when  a  louder  blast 
Shook  beam  and  rafter  as  it  passed, 
The  merrier  up  its  roaring  draught 
The  great  throat  of  the  chimney  laughed." 

However,  we  should  not  overlook  the  fact  that  all  other 
rooms  in  this  typical  farm  home  were  probably  icy  cold,  and 
that  with  all  the  lavish  use  of  wood  as  fuel  in  the  big-throated 
fireplace,  costing  as  it  did  little  more  than  the  labor  incident 
to  cutting  and  hauling  it,  there  was  none  of  the  comfort 
enjoyed  by  us  in  the  even  temperatures  so  easily  maintained 
in  all  parts  of  our  present-day  homes. 


AT  OUR  HOMES 


215 


The  poet  in  his  later  years  could  well  forget  that  in  the 
big  living  room  of  his  boyhood  days,  with  face  burning  from 
the  heat  of  the  open  fire,  there  was  scarcely  a  place  where 
his  feet  at  the  same  time  were  not  chilled  in  the  rush  along 
the  floor  of  cold  air  from  every  doorway  crack  to  feed  the 
chimney's  draft.  In  memories  of  the  "Dear  home  faces 
whereupon  the  fitful  firelight  paled  and  shone"  the  hard- 
ships incident  to  a  winter's  cold  in  the  homes  of  those  early 
days  were  doubtless  forgotten. 


FIG.  69. — Birthplace  of  Elias  Howe,  inventor  of  the  sewing  machine. 

In  time  the  woodlands  were  largely  cleared  for  cultivation, 
the  trees  it  may  be  having  been  burned  just  to  get  rid  of  them- 
The  old-fashioned  fireplace  was  closed.  More  and  more 
generally  from  about  1830  onward  stoves  began  to  come  into 
use  as  heaters  and  for  cooking  purposes.  Coal  as  a  fuel  was 
discovered  in  Pennsylvania  about  1820.  The  rapid  increase 
in  amounts  used  for  industrial  purposes,  however,  dates  from 
about  1880. 

The  production  and  distribution  of  the  enormous  amounts 


2l6 


GENERAL  SCIENCE 


of  coal  now  required  in  the  United  States  at  prices  which  on 
the  one  hand  shall  not  affect  disastrously  the  varied  indus- 
tries of  the  country  dependent  upon  steam  power,  and*  on 
the  other  the  comfort  of  the  people  in  their  home  life,  con- 
stitutes a  "fuel  problem"  likely  to  continue  till  the  natural 
resources  of  the  country  in  its  coal  deposits  shall  have  become 
exhausted. 

nil  lion  Tons 


500 


JOO 


£00 


IOO 


\l\l\\\\\ 

FIG.  70. — Production  of  coal  in  the  United  States  1830  to  1910. 

Without  coal  as  a  fuel,  and  without  any  available  substi- 
tute for  it  in  ample  quantity,  practically  all  the  machinery 
of  modern  life  must  come  to  a  standstill.  Factories,  shops, 
mills,  furnaces,  together  with  railway  and  steamship  lines, 
cannot  be  operated  on  the  same  scale  as  now.  Commerce, 
transportation,  and  manufactures  will  return  to  the  lower 
volume  of  an  earlier  age,  and  present-day  standards  of  living 
will  likewise  be  lowered.  That  this  may  not  come  to  pass 
other  motive  power  than  steam  more  and  more  must  come 
into  use. 

Coal  as  dug  from  the  earth  is  carbon  in  varying  per  cent  of 
purity.  Its  structure  gives  ample  evidence  of  its  being  the 


AT  OUR  HOMES  217 

remains  of  plant  growths.  The  coal  age  in  the  earth's  his- 
tory as  given  in  Geology  must  have  been  a  time  when  climatic 
conditions  were  unlike  those  of  the  present  day.  Vegetation 
grew  rank  in  an  atmosphere  warm,  and  laden  with  moisture 
and  carbon  dioxide.  During  long  periods  of  time  accumula- 
tions of  woody  material  of  great  thickness  must  have  been 
kept  from  decay  by  submergence  in  the  waters  of  marshy 
regions.  Under  the  pressure  of  layers  of  earthy  material 
washed  in  upon  it,  this  vegetable  matter  largely  shut  away 
from  the  air  became  changed  in  course  of  time  into  the  varied 
forms  with  which  we  are  familiar  as  coal.  The  several  layers 
(" veins")  of  coal,  separated  by  layers  of  slate  or  other  rock 
material,  represent  successive  periods  of  accumulation  and 
of  submergence.  Through  later  periods,  and  probably  when 
vegetation  did  not  flourish  so  luxuriantly,  these  thicknesses 
of  vegetable  matter  became  buried  in  the  depths  where  as 
coal  they  are  now  found. 

It  should  be  mentioned  here  that  all  this  carbon  represents 
" stored  solar  energy''  used  by  plants  in  the  separation  of  the 
carbon  from  the  carbon  dioxide  of  the  air.  Enormously 
long  periods  of  time  must  have  been  involved  in  this  forma- 
tion of  the  coal  layers  so  nearly  indispensable  to  the  welfare 
of  mankind.  It  is  calculated  that  at  the  present  rate  of 
increase  in  the  production  and  use  of  coal  the  world's  supply 
will  become  exhausted  in  somewhat  more  than  a  hundred 
years.  Long  before  then,  however,  unless  other  forms  of 
energy  are  employed  for  doing  the  world's  work,  the  rise  in 
prices  due  to  a  limited  supply  is  likely  to  make  them  prohibi- 
tive for  most  people. 

All  means  for  illumination  in  common  use  in  homes  depend 
upon  the  fact  that  when  the  temperature  of  a  substance  has 
been  raised  sufficiently  high  it  becomes  incandescent,  i.e., 
it  gives  out  light.  In  candle,  kerosene  lamp,  and  illuminating 
gas  flames  the  carbon  particles  present  in  the  gas  or  vapor 


218  GENERAL  SCIENCE 

are  made  incandescent  by  the  heat  of  combustion  as  the 
vapors  and  gases  burn.  In  the  incandescent  and  arc  electric 
lights  the  incandescence  is  caused  by  electrical  energy  being 
transformed  into  heat.  Much  resistance  is  offered  to  the 
passage  of  the  electricity  in  the  filaments  of  one,  and  through 
the  air  gap  separating  the  carbon  pencils  of  the  other.  The 
intimate  relationship  believed  to  exist  between  heat  and 
light  as  forms  of  energy  is  shown  in  the  explanation  that  as 
the  temperature  of  a  body  rises  by  reason  of  increase  of  its 
molecular  activity  there  comes  a  time  when  the  ether  dis- 
turbances originating  in  the  quickened  movements  of  its 
molecules,  and  radiating  outward  from  the  body  in  straight 
lines  in  every  direction,  become  sufficiently  frequent  per 
second  to  affect  the  optic  nerves  in  our  eyes,  resulting  in  a 
sensation  of  light  and  enabling  us  "to  see."  Bodies  from 
which  these  light  waves  originate  are  said  to  be  luminous. 
Most  bodies  about  us  are  non-luminous,  and  we  see  them 
only  because  light  coming  to  them  is  reflected  to  us  and  into 
our  eyes.  Much  of  the  expense  of  artificial  lighting  systems 
lies  in  the  fact  that  there  is  large  waste  involved  in  production 
of  the  heat  necessary  to  incandescence.  Illumination  by 
"cold  light,"  i.e.,  at  temperatures  as  low  as  that  of  the  light 
emitted  by  fireflies,  would  greatly  increase  the  comfort  and 
cheapen  the  cost  of  household  illumination. 

SUMMARY 

The  plumbing,  heating,  and  lighting  of  modern  American  homes 
exhibits  in  a  striking  way  the  contributions  of  scientific  achievement 
and  inventive  genius  to  the  comfort  and  well-being  of  this  generation. 
The  homes  of  our  grandparents,  and  the  palaces  of  kings  a  century 
ago,  lacked  these  things.  What  we  now  consider  necessary  to  our 
well-being  they  had  not  dreamed  of. 

Coal  like  the  other  natural  resources  of  timber,  ores,  petroleum,  and 
natural  gas,  is  not  exhaustless  in  quantity.  As  a  source  of  power  by 
reason  of  the  heat  liberated  when  it  is  burned,  coal  is  at  present  indis- 


AT  OUR  HOMES  219 

pensable  in  the  industries  and  in  commerce.  The  heat  liberated  from 
it  may  be  considered  solar  energy  stored  during  the  centuries  of  a 
remote  past. 

It  was  not  till  about  1880  that  the  "incandescent"  light  with  its 
carbon  filaments  within  an  exhausted  glass  bulb,  perfected  by  Thomas 
A.  Edison  (1847 —  — )>  became  a  commercial  success.  The  extended 
use  of  the  powerful  arc  lights  for  out-of-door  illumination  waited  upon 
the  development  of  the  dynamo  to  maintain  sufficient  strength  of 
current  through  long  periods  of  time  at  relatively  low  cost. 


SOME  FOODSTUFFS 

There  is  much  more  to  any  consideration  of  what  one  shall 
eat  and  what  one  shall  drink  than  is  involved  in  its  market 
price  as  part  of  the  cost  of  living,  and  its  purity  and  whole- 
someness  as  these  affect  one's  health.  How  much  to  eat 
(or  how  little),  and  the  relative  amounts  of  the  different 
foods1  in  order  to  give  a  balanced  ration,  are  too  often  given 
scant  attention  till  ill-health  and  its  limitations  make  orders 
from  the  physician  imperative. 

A  person's  appetite  naturally  is  not  only  nature's  warning 
of  need-  for  food  by  the  body,  but  under  normal  conditions 
it  should  serve  as  a  guide  in  choice  of  the  foods  best  suited 
to  meet  these  body  needs.  That  which  is  appetizing,  and 
for  which  one  has  great  relish,  is  in  general  good  for  one. 
Unfortunately  the  appetite  may  become  perverted  or  dulled, 
and  its  guidance  alone  is  always  unsafe.  The  use  of  any 
food  or  drink  that  creates  a  craving,  and  which  demands  more 
and  more  use  of  it  (any  " habit- forming "  substance),  is 
always  to  be  shunned.  One  should  never  eat  beyond  his 
ability  to  fully  digest  what  is  eaten.  Any  meal  is  sufficient 

1  The  term  food  as  used  here  and  later  is  to  be  distinguished  from  "food- 
stuffs" as  sold  in  the  market,  and  the  various  " dishes"  served  at  table  for  our 
meals.  It  has  reference  to  the  groups  of  chemical  compounds  named  on 
page  222. 


22O 


GENERAL  SCIENCE 


where  one  can  work  to  the  next  meal  time  without  becoming 
exhausted  in  strength  or  ravenous  in  appetite.  When  people 
are  well  any  lack  of  appetite  should  generally  mean  absence 
of  bodily  need  for  food.  As  a  rule  it  is  better  to  stop  eating, 
especially  when  the  meal  has  been  at  all  hurried,  before 
being  quite  fully  satisfied  in  hunger. 


<. 

vo  ?\>  v>i  <A  ^  A  -s  o  ^x  o»  <o  C.C//LJ 

Oranges  .... 

Bananas.  .  . 

.Salt  perk.  .  . 

Celery  
Apples  
Canned  corn 
Oysters  
Eggs  

| 

=±F 

Cabbage  
Beef,  sirloin. 
Ham  

•m 

mm 

••  • 

•I 

Mutton  .... 
Turnips  .... 
Rice 

mm 

mm 

mt 

m 

Milk  

• 

Potatoes.  .  .  . 
Beef,  dried.  . 
Pork  loin.  .  . 
Beef,  round. 
Wheat  bread 
Wheat  cereal 
Cheese  
Salmon  
Codfish,  salt 
Beef  stew.  .  . 
Corn  meal.  . 
Oatmeal  
Beans  .  . 

mm 
mm 
mm 
mm 
mm 
mm 
mm 
mm 

m 

I 

i 

i 

; 

FIG.  71. — Comparative  cost  of  the  same  amount  of  protein  from  different  food- 
stuffs1.    (After  Weed.) 

Poor  cooking,  improper  combinations  of  foodstuffs,  and 
use  of  substances  unfit  for  food  because  indigestible,  are 
all  responsible  for  much  ill- health.  It  is  very  likely,  however, 
that  even  more  human  wretchedness  and  sacrifice  of  lives 
comes  from  over-eating.  The  very  poor  often  suffer  greatly 

1The  prices  of  foodstuffs  both  in  general  and  in  relation  to  one 
another  have  been  wholly  changed  as  result  of  the  world  war.  This, 
however,  does  not  impair  the  worth  of  this  exhibit  of  relative  values 
under  normal  conditions. 


AT  OUR  HOMES 


221 


from  lack  of  nutrition  because  of  inability  to  purchase  food. 
But  very  often  it  is  ignorance  of  what  is  most  nutritious 
and  best  to  get  with  the  money  available  that  is  responsible 
for  the  suffering. 

Where  well-to-do  and  ordinarily  intelligent  people  are  not 
normal  in  health,  and  not  free  from  disorders  and  ailments 


. ^Cents 

Oysters 

Celery 

Oranges 

Eggs 

Fish,  fresh 

Beef,  dried.  .  .. 

Bananas 

Sirloin  beef  .  .  . 
Corn,    canned. 

Mutton 

Cabbage  

Salt  codfish.  .  . 
Beef,  round.  .  . 

Ham 

Salmon, canned 

Pork  loin 

Milk 

Apples 

Cheese 

Turnips 

Beef  stew 

Butter 

Rice 

Potatoes 

Wheat  bread .  . 
Wheat  cereal.. 

Salt  pork 

Corn  meal.  . .  . 

Beans 

Oatmeal 

FIG.  72. — Comparative  cost  of  the  same  amount  of  energy  from  different  food- 
stuffs.     (After  Weed.) 

directly  traceable  to  over-indulgence  in  foods,  it  is  a  reflec- 
tion upon  their  judgment  and. self- restraint.  Foods  may  be 
unsuited  to  an  individual  in  their  quality  and  quantity,  or 
because  of  conditions  under  which  they  are  eaten.  In  many 
cases  of  ill-health  the  mischief  was  done  during  the  years 
of  childhood  and  infancy,  and  before  the  years  of  discretion 
had  been  reached.  During  youth,  as  well  as  in  later  years, 


222  GENERAL  SCIENCE 

simple  living  as  to  foods  and  drink  is  commonly  a  sensible 
manner  of  life.  In  these  respects  as  with  amusements  and 
recreations  the  course  of  life  in  general  should  be  to  reject 
whatever  harms  or  leads  to  injury. 

The  foods  may  be  grouped  sufficiently  for  our  purposes 
into  fats  and  oils,  carbohydrates  (such  as  starch  and  sugar), 
and  protein  foods.  Water  and  certain  mineral  salts  are 
also  considered  foods.  The  fats,  oils,  starch,  and  sugar  may 
be  regarded  as  fuels  for  the  body,  and  source  of  a  large 
portion  of  its  energy.  When  they  are  oxidized  the  heat 
liberated  maintains  the  body  temperature.  The  protein 
foods  are  largely  the  tissue-building  material.  They  con- 
tain the  chemical  elements  carbon,  hydrogen,  oxygen, 
and  nitrogen,  with  small  quantities  it  may  be  of  sulphur, 
phosphorus,  and  a  few  other  elements.  The  most  familiar 
foodstuffs  rich  in  proteins  are  the  albumen  in  eggs,  gluten 
in  grains,  legumen  in  beans,  myosin  in  meats,  and  casein  in 
milk.  The  chemical  composition  of  some  of  the  proteins 
is  much  the  same  as  that  of  protoplasm  into  which  they  are 
easily  changed  in  the  body  cells.  The  carbohydrates  cannot 
be  converted  into  protoplasm.  The  nitrogen,  sulphur, 
phosphorus,  and  other  elements  are  obtained  by  plants  from 
compounds  of  them  in  solution  in  the  sap  water.  Soils 
deficient  in  soluble  compounds  of  these  elements  may  have 
their  fertility  restored  by  application  of  fertilizers  containing 
the  necessary  chemical  compounds. 

A  " balanced  ration"  takes  into  account  the  needs  of  the 
body  for  repair  and  growth,  for  warmth  and  energy,  and  for 
maintenance  of  a  state  of  health.  It  seeks  to  approximate 
the  relative  proportions  of  the  foodstuffs  needed  by  the  body 
at  all  times,  and  to  vary  the  proportions  to  suit  the  condi- 
tions of  season  and  employment  as  these  change  from  time 
to  time.  It  is  impractical  to  undertake  to  do  more  than 
approximate  any  exact  balance  in  the  foods  of  which  we 


AT  OUR  HOMES 


223 


make  choice  at  different  times.  However,  it  is  not  only 
possible  but  it  is  indispensable  for  the  maintenance  of  good 
health  to  observe  in  a  general  way  the  required  proportions, 


FIG.   73. — Composition  of  some  common  fatty  foods. 

especially  when  the  diet  suffers  little  change  from  day  to  day. 
The  proportion  of  the  foods  as  classified  above  may  be  stated 
in  a  most  general  way,  and  subject  to  changes  due  to  age  and 


224  GENERAL  SCIENCE 

other  reasons,  as  five-sevenths  carbohydrates,  one-seventh 
fats  and  oils,  one-seventh  proteins.  In  cases  of  illness,  and 
of  convalescence  afterward,  the  maintenance  of  this  balance, 
or  a  departure  from  it  under  direction  of  a  physician,  becomes 
a  matter  of  greatest  importance.  The  amount  of  water  per 
day  taken  as  drink  should  be  from  three  to  five  pints  and  is 
best  taken  between  meals.  Water  with  meals  is  beneficial, 
but  food  should  never  be  "washed  down"  in  place  of  being 
thoroughly  masticated  and  mixed  with  saliva  before  swallow- 
ing. To  habitually  follow  the  practice  of  drinking  a  half 
pint  of  water  or  more  the  last  thing  before  retiring  at  night 
and  the  first  thing  after  rising  in  the  morning  is  an  excellent 
rule  for  health. 

Though  we  may  not  always  know  the  proportions  of  food 
required  to  supply  bodily  needs,  for  people  in  good  health  an 
approximation  to  a  balanced  ration  is  to  serve  at  a  meal 
(a)  one  dish  that  is  largely  starch,  such  as  potato,  rice,  or 
cereal;  (b)  one  rich  in  protein,  such  as  meat,  eggs,  cheese,  or 
beans;  (c)  some  fats,  such  as  butter^  or  fat  meat,  and  some 
sugar  (perhaps  in  fruit  jellies  and  preserves,  or  as  molasses). 

SUMMARY 

Chief-  among  the  protein  foods  are  albumen  in  eggs,  gluten  in  the 
various  grains,  legumen  in  peas  and  beans,  myosin  in  meat,  and  casein 
in  milk.  These  are  composed  chiefly  of  hydrogen,  oxygen,  carbon, 
with  some  nitrogen,  and  in  the  egg  a  little  sulphur.  Other  chemical 
elements  are  present  in  small  quantities  only. 

Some  minerals  in  solution  in  drinking  waters,  and  in  the  cereals  and 
other  foods,  serve  to  keep  the  organs  of  digestion  active  and  the  diges- 
tive fluids  abundant.  Three  to  five  pints  of  water  daily  contributes 
toward  maintaining  a  normal  condition  of  Digestion  and  circulation, 
and  the  elimination  of  waste  from  the  body. 

The  introduction  into  milk  of  some  acid  coagulates  the  casein. 
The  rennet  used  in  cheese-making  is  a  dried  portion  of  the  stomach 
from  a  calf,  and  it  contains  some  of  the  acid  secreted  there  for  use  in 
digestion.  The  gastric  fluid  in  the  human  stomach  contains  a  little 


AT  OUR  HOMES 


225 


From  such  a  table  as  that  below  suggestions  of  choices  may  be 
had,  as  well  as  a  knowledge  of  the  relative  food  values  of  different 
foodstuffs. 

APPROXIMATE  COMPOSITION  or  FOODSTUFFS 


Food  Materials 
(edible  parts) 

Water 
per 
cent 

Protein 
per 
cent 

Fat 
per 
cent 

Carbo-! 
nydrate 
per 
cent 

Ash 
per 
cent 

Heat  value  of 
one  pound 
(in  calories) 

83-2 
75-3 

12.6 

60.0 
68.2 
88.6 

!0-5 

Qi-5 
94-5 
30.2 
80.9 
72.7 
15-0 
73-8 
94-7 
10.3 
87.0 
7.6 
88.0 
87.1 
87.1 
9.0 
50.3 

12.  I 
78.9 
12.4 
90.O 
89.0 
2  .0 

95-3 
12.5 
i3-i 

0.4 

1-3 
22.5 
18.9 
21.3 

2-3 
I  .0 

1.6 
i  .1 

25-9 
i  .0 

21.5 
9-2 

13-4 

I  .  2 
13-4 

3-3 
16.1 
1.6 
0.8 

6.2 

25-8 
17-3 
0.9 

2  .  2 
8.0 
I  .0 
2-3 

0-5 
0.6 
1.8 
18.5 
7-9 

O.  I 

85.0 
0-3 

O.  I 

33-7 
0.8 

2-5 
1.9 

io-5 
0-3 
0.9 
4-0 

7-2 

0-3 

O.  2 
I  .  2 
38.6 

3I-I 

82.8 
O.  I 

o-3 
0.6 

o-3 

14.2 

22  .O 

59-6 
7-4 

I  .0 

5-6 
3-3 
2.4 
16.7 

0-3 
0.8 

3-i 
i  .0 

I  .  2 

1.6 

o-3 
i  .0 
i  .0 
4.2 
0.6 
i-3 
i-4 

I  .0 

0.9 

i-3 

0.7 

2  .O 

2.0 
2  .O 
0.9 
4.2 
I  .0 
0.4 

0-3 

o-3 
0-5 
1.8 

285 
447 
1565 
1099 
709 
1  80 
349i 
143'  . 
84 
1890 

354 
493 
1620 
672 

87 
1625 

314 
1811 
220 

233 
228 
2490 
1585 
3555 
378 
i59i 
169 
184 
1815 
104 
1608 
1628 

Bananas                     

Beans  dry                        .... 

Beef,  sirloin  
Beef   round             

Beets  cooked                    .    .  . 

Butter            

Cabbage  
Celery 

Cheese    cream    

Cherries                               .  .  . 

Chicken 

Cornmeal  
EETGTS 

75-4 

2-9 

74.1 
5-o 
67-5 
9-9 
n.  6 

3-7 
24.4 

18.4 
79.0 

7-4 
7-4 
97-8 
3-9 
74-8 
i7!-4 

Lettuce  
Macaroni  
Milk 

Oatmeal  

Onions 

Oranges 

Oysters  
Peanuts 

Pork,  shoulder  
Pork,  salt  
Potatoes 

Rice  
Strawberries  
String  beans 

Sugar  
Tomatoes,  fresh  
Wheat   flour 

0.9 

10.8 
13-3 

0.4 
i  .  i 

2.  2 

Wheat,  graham  

226  GENERAL  SCIENCE 

free  hydrochloric  acid.  The  casein  in  curdling  gathers  up  much  of 
the  butter-fat  present  in  the  milt. 

Milk  should  contain  about  4  per  cent  of  butter-fat,  and  86  per  cent 
water.  There  is  considerable  sugar  of  milk  in  it,  a  matter  of  importance 
in  preparing  foods  for  infants. 

In  preparing  sausage  for  sale  it  is  a  common  practice  to  mix  in  with 
the  lean  and  fat  meat  as  ground  together  more  or  less  of  starchy  mate- 
rial. As  a  "filler"  this  increases  the  weight  of  the  product,  and  at  the 
same  time  by  absorption  of  the  moisture  contributes  to  the  keeping 
quality  of  the  sausage.  It  is  a  cheaper  material  than  meat,  and  so 
may  be  regarded  as  an  adulterant.  The  use  of  preservatives  in  meats 
interferes  with  their  digestion  when  eaten,  and  they  may  be  positively 
harmful  in  the  system. 

THE  CARBOHYDRATES 

The  botanist  notes  in  the  green  coloring  of  vegetation  the 
presence  of  chlorophyll.  The  little  bodies  containing  this 
chlorophyll  as  found  in  the  protoplasm  of  the  cells  of  the 
plant  are  known  as  chloroplasts.  In  them  the  water  from 
the  ground  and  the  carbon  dioxide  from  the  air  are  being 
manufactured  directly  or  indirectly  into  sugar,  starch,  and 
cellulose  (wood  fibre)  by  use  of  the  energy  derived  from  sun- 
light. Animals  appropriate  and  use  these  products  of 
chemical  change  in  plants,  but  only  plants  can  produce  them 
from  the  raw  materials! 

It  has  been  found  by  botanists  that  plants  as  well  as 
animals  must  have  oxygen  to  live,  i.e.,  to  maintain  the  life 
of  the  protoplasm.  A  product  of  the  processes  of  plant 
life  as  a  whole  is  a  relatively  small  quantity  of  carbon 
dioxide  gas.  This  shows  that  the  process  of  oxidation  goes 
on  in  plants  even  as  in  animals,  though  much  more  slowly. 
During  the  daytime,  and  under  the  influence  of  sunlight, 
this  action  may  be  completely  masked  by  the  fact  that 
carbon  dioxide  obtained  from  the  air  is  at  the  same  time 
being  chemically  combined  with  water  in  the  plant.  A  prod- 
uct of  this  change  is  a  relatively  large  amount  of  oxygen 


AT  OUR  HOMES  227 

given  back  into  the  air.  It  is  in  this  way  that  the  large 
amounts  of  oxygen  gas  withdrawn  from  the  air  by  respiration, 
by  decay  of  vegetation,  and  by  the  combustion  of  wood 
and  coal,  are  returned  to  it,  and  the  per  cent  of  oxygen  in  the 
air  maintained  practically  unchanged. 

Neither  botanists  nor  chemists  undertake  to  say  definitely 
just  how  the  changes  occur  in  the  chloroplasts,  nor  the  exact 
nature  of  the  chemical  products  at  successive  stages  of  these 
changes.  It  is,  however,  an  aid  to  an  understanding  of 
the  chemical  relationship  between  the  products  of  chloro- 
phyll activity  by  assuming  that  it  can  be  expressed  in  this 
way: 

CO2  +  H2O  =  O2  +  CH2O 

The  CH20  may  be  considered  a  compound  of  carbon  and 
water,  and  is  type  of  the  compounds  known  as  carbo- 
hydrates, of  which  starch,  sugar,  and  cellulose  are  familiar* 
examples. 

Assuming  this  change  to  have  taken  place,  the  chemical 
relationship  of  these  carbohydrates  becomes  more  apparent 
by  a  comparison  of  their  chemical  formulae,  rewritten  with 
reference  to  the  CH2O  group  of  atoms  : 


Starch  .................  (CeH^)*1  =  (6CH2O  -  H,O} 

Grape  sugar  ............       C6H:2O6  =  6CH2O 

Cane  sugar  .............  Ci2H22Oii  =  i2CH2O  -  H2O 

Cellulose  ...............  (CeHioOs)/  =  (6CH2O  - 


These  hypotheses  conform  quite  closely  to  what  is  known 
about  these  substances. 

1  The  subscripts  x  and  y  are  some  unknown  but  definite  numbers  of  these 
groups.  By  conceiving  the  molecules  of  starch  and  of  cellulose  to  be  made  up 
of  different  numbers  of  groups,  and  these  groups  arranged  in  different  com- 
binations (even  as  the  same  kind  of  bricks  may  be  built  together  to  form 
entirely  different  structures),  it  is  possible  to  account  for  such  different  sub- 
stances as  starch  and  cellulose  even  when  made  up  of  the  same  chemical 
elements  united  in  the  same  proportions  by  weight. 


228  GENERAL  SCIENCE 

Starch  is  lacking  in  solubility  in  cold  water,  while  the 
sugars  are  easily  dissolved.  It  would  seem  probable  that 
whichever  carbohydrate  may  be  the  direct  product  of  the 
building-up  process  under  the  influence  of  light,  photo- 
synthesis as  it  is  called,  the  distribution  of  this  product  through 
the  tissues  of  the  plant  for  use  as  food  or  for  storage  involves 
changes  from  starch  to  sugar  and  then  again  to  starch. 
These  changes,  apparently,  are  easily  accomplished  in  the 
plant  economy. 


FIG.  74. — Starch  cells  of  potato  showing  granules  within  cellulose.  When 
cooked  these  granules  swell  and  burst  open,  a  condition  favorable  for 
digestion. 


There  are  very  many  examples  in  Chemistry  of  substances 
entirely  unlike  one  another,  but  having  the  same  elements 
in  them  united  in  the  same  proportion  by  weight.  The  most 
satisfactory  explanation  of  their  differences  in  properties 
is  a  supposed  difference  in  the  arrangement  of  atoms  in  the 
make-up  of  their  molecules. 

In  the  processes  of  digestion,  too,  while  starch  and  sugar 
are  foods  of  greatest  value  and  readily  digested  ordinarily, 
the  cellulose  is  very  largely  indigestible.  Long-continued 
cooking  softens  and  to  some  extent  makes  available  small 
portions  of  the  cellulose  of  vegetables  and  grains.  A  certain 
amount  of  cellulose  in  our  foods  is  of  great  value,  however, 
in  giving  bulk  to  it,  i.e.,  in  making  it  less  concentrated. 


AT  OUR  HOMES  229 

This  stimulates  a  desirable  activity  of  the  muscles  of  the 
digestive  tract. 

In  the  starch  of  potato,  rice,  corn  (maize),  and  the  various 
small  grains  used  by  man  as  foods,  there  is  appropriated 
by  him  what  the  parent  plant  had  stored  for  the  use  of  the 
young  plants  of  a  succeeding  generation.  In  the  develop- 
ment of  a  young  plant  in  the  process  of  germination,  this 
stored  starch  becomes  changed  into  soluble  grape  sugar. 
The  chemist  and  the  botanist  are  baffled  in  their  understand- 
ing of  just  how  these  changes  are  accomplished. 

The  common  potato  is  largely  starch  and  water.  Unlike 
the  grains,  which  are  seeds  containing  the  embryos  of  new 
plants,  the  potato  is  considered  an  underground  stem  very 
much  shortened  and  thickened.  In  it  there  is  a  storage  of 
starch  to  start  out  the  new  growths  of  potato.  The  "eyes" 
of  the  potato  are  buds  from  which  are  developed  roots  and 
stems.  These  as  new  plants  depend  for  their  first  growth 
upon  the  stored  food  of  the  tuber  (thickened  stem). 

The  beet  is  type  of  a  class  of  plants  which  store  a  food 
supply  for  the  next  season's  growth  in  their  roots.  These  are 
much  thickened  as  a  result  of  this  storage.  These  beet 
roots  when  set  out  a  second  season  grow,  blossom,  and 
produce  seeds  for  the  perpetuation  of  their  species.  This 
growth  of  stalk  and  flower  and  seeds  makes  use  of  the  stored 
food  of  the  past  season's  growth.  In  the  case  of  the  sugar 
beet  the  stored  sugar  is  chemically  like  that  in  the  stems  of 
sugar  cane  and  sorghum.  There  is  enough  of  it  to  make  its 
extraction  from  the  sliced  beet  roots  profitable.  Enormous 
quantities  of  beet  sugar  are  produced  in  Germany,  France, 
and  the  United  States. 

In  the  seeds  of  corn  and  cotton  and  flax,  as  well  as  in  cer- 
tain fruits  such  as  olives  and  various  kinds  of  nuts,  a  supply 
of  food  in  the  form  of  oil  is  stored  for  the  young  plant 
when  germination  shall  occur.  In  other  cases  as  in  peas, 


230 


GENERAL  SCIENCE 


FIG.   75. — The  common  potato. 


AT  OUR  HOMES  231 

beans,  and  the  gluten  of  grains,  there  is  formed  the  complex 
compound  known  as  protein. 

SUMMARY 

Starch  arid  cellulose  are  made  up  of  the  elements  carbon,  hydrogen* 
and  oxygen,  and  these  are  in'the  same  proportions  by  weight  in  both 
substances.  Ordinarily  this  would  mean  that  any  two  bodies  of  which 
this  is  true  are  one  and  the  same  substance.  But  starch  and  cellulose 
have  entirely  different  properties  and  are  recognized  as  entirely  sepa- 
rate substances.  While  starch  is  one  of  the  chief  foods  of  mankind, 
cellulose  is  indigestible  and  is  familiar  to  us  in  such  forms  as  cotton  and 
linen  (flax)  fibre,  wood,  paper,  etc. 

The  most  reasonable  explanation  of  the  production  of  different 
substances  from  the  same  proportions  by  weight  of  the  same  elements 
is  that  the  ways  in  which  the  atoms  have  been  put  together  must  be 
unlike.  In  the  studies  of  chemical  compounds  of  plant  or  animal 
origin  cases  of  this  kind  are  not  uncommon. 

Plants  under  the  influence  of  sunlight  can  manufacture  their  own 
food  as  starch  and  sugar  out  of  the  raw  materials  of  water  and  carbon 
dioxide  gas.  They  may  store  any  excess  of  it  in  root,  stem,  leaf,  seed, 
or  fruit.  Probably  it  is  in  the  form  of  sugar  only  that  it  is  conveyed 
in  the  sap  of  the  plant  from  where  it  is  made  to  where  it  is  stored,  and 
then  again  to  where  it  is  needed  later  for  the  growth  of  the  plant  and  the 
maturing  of  its  seeds. 

The  accomplishment  of  this  change  back  and  forth  of  starch  and 
sugar,  and  their  change  into  cellulose  in  the  woody  part  of  the  plant 
structure,  is  not  well  understood  by  either  botanists  or  chemists.  The 
substance  made  by  the  plant  known  as  diastase  is  probably  concerned 
in  these  chemical  changes  in  the  life  processes  of  the  plant. 

In  some  plants  along  with  the  starch  stored  as  food  for  the  plant  is 
more  or  less  of  vegetable  oils.  Olive,  cocoanut,  cottonseed,  and  lin- 
seed (flaxseed)  oils  are  good  illustrations.  Many  different  kinds  of 
nuts  contain  oil  enough  to  be  very  noticeable  when  the  pulp  is  crushed. 

The  presence  of  starch,  especially  after  having  been  boiled  in  a  little 
water,  is  made  known  by  a  characteristic  blue  coloration  when  treated 
with  a  little  weak  iodine  solution.  (See  page  301  for  test  for  proteins.) 

When  a  few  drops  of  Fehling's  solution,  whose  blue  color  is  due  to 
the  presence  in  it  of  a  compound  of  copper,  is  added  to  a  solution  con- 
taining any  grape  sugar  or  glucose  and  heated,  the  blue  color  disappears 


232 


GENERAL  SCIENCE 


and  a  yellowish  (and  perhaps  reddish)  precipitate  forms.  Cane  sugar 
does  not  give  this  result  with  the  Fehling  solution,  although  some  few 
other  less  common  sugars  do. 

Exercises 

1.  Name  various  grains  having  extensive  use  as  foodstuffs.     What  others 
are  less  commonly  used? 

2.  Name  the  two  food  elements  constituting  the  larger  part  of  the  grains. 

Wherein  does  the  food  value  of  wheat  exceed  that  of  an  equal  weight  of 
corn? 


FIG.   76. — Boiling  maple  sap.     The  old  way  of  making  maple  syrup. 

3.  Name  several  foods  other  than  the  grains  that  are  rich  in  starch.     What 
is  the  chemical  test  (a)  for  starch;  (b)  for  gluten;  (c)  for  sugar? 

4.  What  purpose  is  served  by  the  gluten  of  wheat  flour  in  the  making  of 
loaves  of  bread?     Wherein  lies   the  difficulty  experienced  in  making 
bread  from  corn  or  rice  flour? 

6.  What  is  the  purpose  of  yeast  in  bread  making?  What  advantage  in  its 
use  over  baking  powder?  Why  is  the  flour  for  bread  moistened  with 
water,  and  the  dough  " raised"  in  a  warm  place?  What  causes  sour 
bread? 

6.  What  is  the  purpose  of  kneading  several  times  the  dough  from  which 
bread  is  to  be  made?  Name  four  important  ends  accomplished  in  the 
baking  of  a  loaf  of  bread. 


AT  OUR  HOMES  233 

7.  What  constitutes  the  cooking  of  starch  in  foods?     What  is  the  nature 
of  the  popping  of  corn,  and  the  baking  of  potato? 

8.  Discuss   the   chemistry  of  starch  formation  in  plants.     What  is   the 
chemical  formula  for  starch? 

9.  What  is  the  chemistry  of  the  digestion  of  starch?     What  need  is  there 
for  any  such  change?     In  the  similar  change  which  occurs  in  seeds  where- 
by the  stored  starch  is  made  available  for  the  young  and  growing  plant 
as  food,  what  is  the  ferment  whereby  this  change  is  brought  about? 

10.  What  is  malt?     Explain  its  use  in  prepared  foods  for  infants. 

11.  Describe  the  steps  in  the  manufacture  either  of  cane  or  of  beet  sugar. 
Why  are  "vacuum  pans"  used  in  boiling  the  syrups? 

12.  Name  two  important  uses  of  starch  in  baking  powder. 

13.  Explain  the  rising  of  a  loaf  of  cake.     Why  does  it  retain  its  form  when 
baked?     What  explanation  is  there  for  "fallen"  cake? 

14.  About  what  per  cent  of  wheat  flour  is  starch? 

15.  Explain  the  ill-effects  of  eating  unripe  fruit.     What  changes  occur  in 
the  ripening  process? 

16.  What  uses  have  (a)  grape  sugar  (as  a  solid);  (b)  glucose  (as  a  liquid)? 
What  is  true  of  the  relative  sweetness  of  cane  and  grape  sugars? 

17.  Learn  from  some  text  in  Chemistry,  or  any  other  source,  the  names  of 

the  several  kinds  of  sugar,  and  the  source  of  each  kind. 

18.  What  deleterious  materials  are  sometimes  used  in  making  candy?     What 

constitutes  excess  in  the  use  of  candy? 

19.  What  ways  are  employed  other  than  drying  and  canning  to  keep  fruits 
for  long  periods  in  a  condition  fit  for  use  as  foods? 

20.  What  "preservatives"  are  sometimes  found  in  jellies  and  canned  goods? 
What  purpose  is  served  in  the  use  of  coloring  materials,  such  as  coal  tar 
dyes,  in  ketchup?     What  effect  upon  the  digestibility  of  foodstuffs  have 
most  of  the  chemicals  used  as  preservatives?     Why  is  this  so? 

21.  Make  a  list  of  the  various  foods  represented  in  the  table  service  of  one  day. 
Then  underscore  all  those  that  are  from  plants. 

22.  What  dietary  conditions  are  met  in  the  use  of  bread  and  milk  as  a  simple 
food? 

FIRES,  BURNS,  AND  VARIOUS  ACCIDENTS 

Perhaps  nowhere  does  the  competency  or  incompetency 
of  an  individual,  his  practical  knowledge  or  lack  of  it,  mani- 
fest itself  so  notably  as  in  times  of  emergency.  While  it  may 
not  be  worth  while  always  to  be  getting  ready  for  the  unusual 
.to  occur,  and  for  what  is  unlikely  to  happen,  yet  the  un- 
expected often  occurs,  and  accidents  are  common.  Avoid- 


234  GENERAL  SCIENCE 

ance  of  lifelong  suffering  and  disability,  even  the  preservation 
of  life  itself,  may  depend  in  emergencies  upon  the  prompt 
and  intelligent  course  of  action  of  some  individual  upon  whom 
responsibility  is  thrust  without  warning. 

In  the  most  urgent  cases  there  is  no  time  and  often  no 
opportunity  to  consult  other  persons  or  to  read  from  books. 
One  must  know  exactly  what  to  do  and  how  it  is  to  be  done, 
and  must  act  without  loss  of  time.  A  fairly  good  substitute, 
however,  for  this  skill  and  knowledge,  and  a  much  better 
course  than  to  act  inadvisedly  just  for  the  sake  of  doing 
something,  is  to  have  some  reliable  book  of  directions  always 
at  hand  for  times  of  emergency.  With  its  contents  one  should 
be  sufficiently  familiar  to  be  able  to  turn  immediately  to  the 
needed  detailed  directions  which  one  cannot  be  expected  to 
remember.  The  book  should  give  this  information  so  briefly 
and  so  clearly  that  it  can  be  read  and  understood  at  a  glance. 
An  inexpensive  booklet,  containing  information  much 
condensed,  printed  in  good  type  and  with  ample  spacings, 
is  more  serviceable  for  general  use  than  a  lengthy  medical 
treatise. 

Instruction  should  be  given  at  home  and  at  school  upon 
what  to  do  before  the  doctor  arrives,  and  what  course  to 
pursue  in  times  of  accident  or  panic.  This  teaching  should 
not  wait  upon  some  deplorable  occurrence  or  some  great  dis- 
aster. Such  instruction  may  very  properly  include  such 
matters  of  common  knowledge  as  these: 

1.  To  free  the  stomach  of  poison,  or  of  undigested  food,  a  simple  house- 
hold emetic  easily  administered  is  a  teaspoonful  of  ground  mustard  well 
stirred  in  a  cup  of  lukewarm  water.     Then  after  a  little  by  thrusting  the 
fore-finger  far  back  in  the  throat  vomiting  may  be  brought  about.     Repeat 
the  treatment  if  deemed  necessary. 

2.  A  good  sterilizing  liquid  into  which  to  place  spoon,  thermometer,  or 
other  small  articles  in  use  by  patients  sick  with  an  infectious  disease,  or  the 
instruments  used  by  dentists  and  surgeons  in  their  practice,  or  by  teachers 
in  examining  the  throats  of  pupils,  is  a  4  per  cent  solution  of  carbolic  acid 
(one  ounce  to  a  quart  of  water). 


AT  OUR  HOMES  235 

3.  A  solution  of  a  pound  of  chloride  of  lime  from  a  fresh) y  opened  can  in 
three  gallons  of  water  is  perhaps  the  cheapest  and  most  effective  disinfectant 
with  which  to  treat  for  twenty  minutes  or  more  all  excreta  before  it  is  thrown 
out  into  sewer,  privy,  or  cesspool. 

4.  One   of  the  best  ways  of  freeing  formaldehyde  gas  from  formalin  for 
disinfecting   purposes  is  to  add  crystals  of  permanganate  of  potash  to  the 
formalin  in    the   proportion  of   one-half  pound  per  pint  of  the  liquid.     The 
dish  containing  the  formalin  should  be  set  in  another  and  larger  dish  in  case 
there  should  be  any  overflow  or  spattering. 

The  enormous  losses  annually  by  fires  in  the  United  States 
constitutes  a  standing  reflection  upon  the  course  of  the  Ameri- 
can people  in  the  conservation  of  their  resources,  and  upon 
their  intelligence  in  not  more  effectively  preventing  these 
wastes.  From  the  long  list  of  reported  causes  of  fires  it  is 
possible  to  ascribe  an  appalling  number  to  heedlessness,  and 
to  an  indifference  to  life  and  property  that  well  may  be  con- 
sidered criminal.  Closely  akin  to  these  is  dishonesty  and 
incompetency  in  the  construction  and  in  the  care  of  build- 
ings. Painstaking  efforts  to  avoid  fires,  and  intelligent  pre- 
cautions against  them,  are  elements  of  an  enlightened  citizen- 
ship. The  insurance  rates  necessarily  charged  to  repay 
losses  by  fire  in  the  United  States  are  a  sad  comment  on  the 
thrift  of  people,  and  constitute  no  small  burden  upon  the 
occupants  of  buildings  whether  as  owners  or  as  tenants. 

While  texts  on  human  biology,  and  various  books  on  what 
to  do  in  case  of  emergency,  give  information  about  burns  and 
their  treatment,  and  how  to  alleviate  suffering  and  to  prevent 
infection,  no  books  or  schools  can  insure  persons  against  the 
results  of  foolhardiness  on  their  own  part  or  on  the  part  of 
others. 

When  kerosene  is  poured  upon  smoldering  coals  a  large 
amount  of  vapor  is  likely  to  form.  This  vapor  mixed  with 
air  is  explosive,  and  requires  only  an  ignition  temperature  to 
result  in  flames  that  reach  outward  as  far  as  the  vapor  has 
diffused.  The  spread  of  the  combustion  throughout  the 
mixture  is  almost  instantaneous.  To  use  gasoline,  benzine, 


236  GENERAL  SCIENCE 

or  naphtha  in  rooms  closed  or  not  thoroughly  ventilated  is  to 
invite  a  like  result  from  ignition  of  its  vapor. 

When  one's  clothing  is  on  fire,  and  when  one  is  enveloped 
in  smoke  or  flame,  a  safe  course  to  pursue  is  to  throw  one's 
self  to  the  floor  where  there  may  be  some  air  to  breathe,  and 
where  the  flames  will  pass  upward  and  away  from  the  body. 
Wrapping  one's  self  closely  from  neck  down  in  several  thick- 
nesses of  blanket  by  quickly  rolling  over  and  over  in  it  may 
smother  the  flames  of  burning  clothing.  Putting  a  wet 
handkerchief  over  the  mouth  and  nose  lessens  the  danger  of 
strangulation  from  smoke. 

Where  the  skin  is  not  broken,  relief  from  the  pain  of  a  burn 
may  be  had  by  putting  the  burned  surface  into  cold  water 
thick  with  baking  soda,  or  by  keeping  the  burned  area 
covered  with  a  paste  of  the  soda.  Later,  soft  cloths  with 
some  soft  ointment  may  be  applied  to  keep  the  skin  soft  and 
moist.  Where  blisters  form,  the  watery  liquid  may  be  re- 
moved by  use  of  a  sharp  needle  that  has  first  been  sterilized 
by  holding  it  a  moment  in  a  flame,  or  dipping  it  into  some 
sterilizing  liquid.  Where  the  skin  is  burned  off  medical 
attention  is  necessary  as  infection  of  the  wound  must  be 
prevented.  In  binding  up  the  wound,  cotton  should  not 
be  put  next  the  wound  because  the  removal  of  the  threads 
later  may  occasion  intense  suffering. 

Burns  seriously  affecting  one- third  or  more  of  the  surface 
of  the  body  are  likely  to  prove  fatal.  This  result  is  not  so 
much  from  the  destruction  of  tissue,  or  from  infection  when 
the  skin  has  been  broken,  as  it  is  from  an  excessive  irritation 
of  the  nerve  terminals  and  a  destructive  shock  to  the  cells 
of  the  nerve  centres.  The  centres  that  stimulate  and  control 
the  organs  concerned  in  respiration,  circulation,  nutrition, 
etc.,  may  be  so  affected  by  the  shock  as  to  fail  to  maintain 
their  activities. 

Many  people  who  have  suffered  accident  of  one  kind  or 


AT  OUR  HOMES  237 

another  are  able,  in  spite  of  suffering  and  limitations,  to  do 
well  their  duties  in  life.  Then,  too,  the  hardships  from  the 
accidents  of  life  oftentimes  reach  beyond  the  sufferer  to 
others  more  or  less  dependent  upon  him.  The  losses  to 
individuals  and  to  society  in  general  by  preventable  accidents, 
where  persons  are  killed  or  maimed  for  life,  astound  those 
who  know  of  their  extent.  It  is  difficult  to  estimate  how 
much  apparently  unnecessary  human  loss  and  human  woe 
is  represented  by  these  accidents. 

The  terrible  sacrifices  of  life  and  health  on  the  soldiery  in 
times  of  war,  and  the  sufferings  and  wretchedness  endured 
as  a  result  of  war  by  the  innocent  and  helpless,  even  of 
generations  unborn,  have  been  endured  by  mankind  through 
all  the  ages.  Though  excused  at  times,  only  in  rare  cases 
are  they  justified.  On  the  other  hand,  there  has  been  a 
growing  demand  in  the  United  States  of  late  years  for  better 
protection  to  the  lives  and  health  of  the  vast  army  of  indus- 
trial workers  engaged  in  peaceful  production  rather  than  the 
devastation  caused  by  war.  These  efforts  have  gone  to 
great  lengths  in  the  exercise  by  society  at  large  of  care  to 
safeguard  workers  against  accident.  The  liability  of  em- 
ployers of  labor  for  any  negligence  in  this  respect  is  coming 
to  be  generally  recognized. 

There  are  many  occupations  in  which  men  are  engaged  in 
order  to  earn  a  livelihood  where  their  health  is  imperiled 
despite  all  precautions  taken  both  by  the  workmen  and  by 
their  employers.  The  lungs  of  the  coal  heaver,  and  of  work- 
men in  cement  factories,  flour  mills,  and  stone  cutting  estab- 
lishments, are  likely  to  become  irritated  by  the  solid  particles 
that  pass  the  guards  established  by  nature  along  the  nasal 
passages.  In  match  factories,  in  the  manufacture  of  illumi- 
nating gas,  and  elsewhere,  men  may  be  harmed  by  foul  and 
poisonous  gases.  Devices  to  protect  life  and  health  lessen 
these  risks  and  may  wholly  eliminate  danger. 


238  GENERAL  SCIENCE 

Perhaps  the  greatest  obstacle  to  any  full  measure  of 
success  in  these  efforts  is  the  culpable  negligence  and  indif- 
ference of  workers  themselves,  and  a  lack  of  the  forethought 
that  makes  accidents  unlikely.  The  " safety  first"  crusade 
in  the  industrial  world  has  sought  to  impress  upon  employees 
having  to  do  with  travel,  transportation,  and  industrial 
life  generally,  the  demand  that  human  life  under  no  circum- 
stances shall  be  put  in  peril.  No  risks  are  to  be  counte- 
nanced under  any  conditions,  and  the  efficiency  of  any 
employee  depends  upon  whether  he  is  trustworthy  as  well 
as  capable. 

A  man  who  drinks,  whose  brain  is  not  clear  and  whose 
judgment  is  warped,  whose  nerves  are  unsteady  and  senses 
dulled,  is  not  wanted  anywhere  in  the  trades,  shops,  factories, 
railway  or  steamship  service,  in  business  houses  or  the  pro- 
fessions, nor  in  any  place  where  property  and  life  are  in  any 
measure  dependent  upon  his  discharge  of  duties.  The  drink- 
ing man,  however  brilliant  in  his  attainments,  is  not  con- 
sidered reliable,  and  the  financial  loss  in  making  good  his 
mistakes  sooner  or  later  costs  him  his  position.  Employers 
of  labor  cannot  afford  the  risk  involved  where  any  man  wil- 
fully imperils  his  own  life  or  that  of  others  in  any  way. 

Railway  corporations  have  long  insisted  upon  the  highest 
degree  of  efficiency  in  locomotive  engineers.  Prepared  for 
service  by  long  training,  steady  of  nerve  and  of  good  judg- 
ment, unwilling  to  take  risks  and  mindful  of  the  responsi- 
bilities resting  upon  them,  these  men  as  a  class  have  won  and 
have  retained  the  confidence  of  the  traveling  public.  Men 
in  charge  of  expensive  steam  and  electric  plants  are  of 
necessity  competent  men,  and  their  license  is  supposed  to  be 
evidence  of  their  fitness  to  discharge  the  responsibilities  of 
their  positions.  Incompetency  manifests  itself  sooner  or 
later,  and  causes  loss  of  license  to  operate  power  machinery. 

One  of  the  features  of  the  introduction  and  general  use  of 


AT  OUR  HOMES  239 

automobiles  as  power  machinery,  operating  at  high  rates 
of  speed  on  public  highways,  has  been  the  distressing  list 
of  fatalities  annually,  amounting  the  country  over  to  an 
enormous  total  in  killed  and  maimed.  " Safety  first" 
needs  to  be  learned  by  each  new  generation  of  automobile 
drivers.  Protection  should  be  assured  to  people  on  the  public 
highways  as  elsewhere  against  incompetency,  recklessness, 
and  an  indifference  to  human  life  and  suffering.  Only  those 
of  proved  competency  in  the  handling  of  machines  should 
be  licensed  to  use  the  highways  of  public  travel. 

SUMMARY 

In  times  of  accident  and  of  danger  it  is  important  to  keep  from  be- 
coming unduly  excited.  Definite  information  of  the  procedure  to  be 
followed  in  times  of  emergency,  whether  in  the  home  or  elsewhere,  is 
knowledge  upon  which  life  itself  may  at  times  depend.  What  to  do 
till  the  doctor  comes  is  knowledge  worth  having. 

Many  fires  are  undoubtedly  accidental.  It  is  extremely  probable, 
however,  that  enormous  annual  losses  by  fire  in  the  United  States  are 
wholly  unnecessary,  and  chargeable  to  carelessness,  shiftlessness,  or 
incompetency.  This  waste  puts  a  heavy  tax  upon  property  holders 
generally,  for  they  must  pay  higher  fire  insurance  premiums  to  cover 
these  unnecessary  fire  losses. 

Death  from  burns  follows  at  times  because  of  the  shock  to  the  nerve 
centres  as  result  of  the  pain  from  the  irritated  nerve  ends.  Especially 
is  this  the  case  when  the  centres  affected  are  those  from  which  originate 
the  impulses  maintaining  action  of  the  heart  and  other  vital  organs. 
Where  the  skin  is  broken  in  case  of  a  burn,  antiseptic  dressings  must 
be  used  for  the  wound  to  prevent  its  becoming  infected. 

In  all  places  in  life,  and  under  all  circumstances,  due  precautions 
to  prevent  accident  are  to  be  insisted  upon.  Indifference  to  the  wel- 
fare of  others  is  selfishness,  and  foolhardiness  in  conduct  shows  lack  in 
good  judgment  and  in  ordinary  good  sense.  Forethought  and  pains- 
taking measures  are  obligations  resting  on  all  persons  alike. 

Exercises 

1.  In  view  of  possible  fires  in  a  factory  building,  what  advantage  is  there  in 
having  the  elevator  shaft  far  removed  from. the  stairways?  Under 
what  circumstances  have  fire-escapes  many  times  failed  to  provide 
means  of  escape  from  burning  buildings? 


240  GENERAL  SCIENCE 

3.  To  what  special  dangers  are  workmen  exposed  (a)  in  mines;  (6)  in  bridge 
building,   and   in   the   erection  of  great  office  buildings;   (c)  in  railroad 
shops;  (d)  in  foundries? 

4.  Name  at  least  four  extra-hazardous  occupations  for  men  employed  indoors. 

5.  Upon  what  day  of  the  week  have  most  accidents  been  found  to  occur? 
What  interpretation  is  placed  upon  this?     What  relation  to  this  has  the 
lesson  on  Rest,  Recreation,  and  Amusements? 

6.  Make  a  list  of  devices  that  very  suitably  may  be  headed  "  For  Safety  First". 
Make  a  list  of  short  rules  and  regulations  for  the  public  designed  to  ac- 
complish this  same  end. 


XI.  SURROUNDINGS  OF  THE  HOME 

THE  GARDEN,  AND  ITS  CARE 

A  home  garden  for  the  dweller  in  town  may  have  a  greater 
worth  to  its  possessor  than  any  mere  savings  in  garden 
produce.  A  healthful  diet  is  very  likely  to  include  for  most 
people  plenty  of  vegetables  in  season,  whether  from  a  garden 
on  the  farm  or  in  town,  whether  raised  by  the  consumer  or 
purchased  in  market.  But  wholly  aside  from  this  fact,  and 
from  the  pleasures  that  come  through  the  care  and  cultiva- 
tion of  growing  plants,  the  physical  exercise  involved  in 
garden  work  is  unexcelled  in  its  benefits.  Out-of-door  work 
in  the  garden  and  on  the  home  premises,  together  with  an 
hour's  walk  a  day,  is  an  amount  of  exercise  that  is  not  only 
desirable  for  the  average  town-dweller,  but  is  usually  possible 
to  anyone  in  connection  with  the  ordinary  round  of  life. 
The  value  of  a  garden  as  a  place  in  which  to  get  physical 
invigoration  and  mental  clearness,  especially  during  the 
morning  hours,  is  too  commonly  underrated.  Regular  hours 
for  labor  that  have  in  them  as  an  incentive  something  that  is 
worth  while  furnish  an  assurance  of  continued  good  health 
and  of  a  life  that  is  efficient  to  the  last.  In  the  commonplace 
affairs  of  everyday  life,  especially  in  connection  with  a  well- 
kept  home  and  its  surroundings,  are  to  be  found  pleasures 
and  contentment  not  possible  elsewhere. 

A  liking  for  plants,  and  an  appreciation  of  their  important 

part  in  the  enjoyments  of  life,  comes  in  large  measure  through 

care  for  them  and  from  the  responsibilities  that  this  care 

involves.     The  boy  or  girl  who  grows  up  in  town  or  city  with- 

16  241 


242 


GENERAL  SCIENCE 


out  having  had  the  care  of  plants  in  yard  and  garden,  and  who 
has  not  learned  to  be  successful  in  the  cultivation  of  vege- 
tables and  flowers,  of  vines  and  shrubs,  has  missed  one  of  the 
humanizing  influences  of  life.  The  care  of  plants  and  of 
domestic  animals  at  home  teaches  much  that  is  of  great  value 
in  the  studies  of  Botany  and  Zoology.  But  its  greatest 


- 


FIG.   77. — Lawn,  shrubbery,  and  trees  as  surroundings  of  a  home. 

educational  value  lies  in  the  sense  of  obligations  assumed, 
and  in  a  regard  for  living  things  that  it  develops. 

Where  the  sciences  of  Botany  and  Zoology  are  taught  to 
pupils  whose  only  knowledge  of  plants  and  animals  is  from 
the  courses  in  the  classrooms  and  laboratories  of  high  schools, 
the  results  are  likely  to  fall  far  short  of  the  possibilities  of 
these  branches  of  study.  Very  much  in  literature  remains 
a  closed  book  to  those  who  during  childhood  and  youth  have 
been  denied  the  birthright  of  a  personal  knowledge  of  plants 
and  of  domestic  animals  gained  through  care  of  them. 


SURROUNDINGS  OF  THE  HOME 


243 


In  the  care  of  a  garden  as  in  the  affairs  of  life  generally 
initiative  is  accounted  an  indispensable  trait  in  any  one  who 
would  succeed.  The  power  of  initiative  is  sometimes  said 
to  be  an  ability  to  see  what  needs  to  be  done,  a  readiness  to 
undertake  it,  and  an  industry  and  perseverance  that  accom- 
plishes what  is  undertaken.  No  success  is  achieved  without 
it  in  any  of  the  pursuits  of  life  whether 
professional,  financial,  social,  or  political. 

Much  of  the  farmer's  success  with  crops 
is  secured  by  doing  on  a  larger  scale  what 
must  be  done  in   the  care  of  a  garden. 
The  soil  must  be  in  suitable  condition  as  a 
seed   bed   that  the    young  and    growing 
plants  may  thrive  from  the  time  the  seeds 
germinate.     It  must  contain  the  needed 
food  material  in  available   soluble  form. 
There  must  be  the  necessary  cultivation 
of  the  surface  soil  so  that  the  supply  of 
moisture    in    the    ground    is    sufficiently 
conserved    to    provide   for   the   needs  of 
the    growing    plants.      Weeds    that    ap- 
propriate   the    supply   of   food  material,    masnified- 
and  that  rob  the  crop  of  available   soil  water  during  the 
growing  season,  must  be  kept  down.     Then,  too,  failure  is 
sure  to  follow  the  use  of  seeds  of  poor  quality  and  of  im- 
paired powers  of  germination. 

Any  cultivation  of  the  soil  must  be  so  suited  to  the  crop 
and  to  changing  weather  conditions  as  to  preserve  a  texture 
in  which  the  rootlets  and  root-hairs  may  everywhere  pene- 
trate it  with  ease.  The  root  system  of  a  tree  is  likely  to  be 
more  wide-spreading  than  its  branches,  with  innumerable 
rootlets  penetrating  in  every  direction  all  the  soil  round 
about  the  tree.  There  is  reason  to  believe  that  when  a  plant 
is  uprooted  even  with  considerable  care  a  very  large  part 


FIG.  78.  —  Root- 
hairs  on  corn  seedling 


244 


-          GENERAL  SCIENCE 


of  its  root  system  breaks  off  and  is  left  in  the  ground.  The 
root-hairs  are  found  just  back  of  the  growing  ends  of  the 
roots.  They  are  it  may  be  but  an  eighth  of  an  inch  or  less 
in  length,  and  are  merely  elongated  cells  of  the  outer  covering 
of  the  rootlets.  They  never  become  roots  but  disappear  as 
the  rootlet  grows  older  and  forms  a  thicker  outer  coat  or 
bark. 


FIG.   79. — The  young  gardener. 

All  labor  and  painstaking  on  the  part  of  a  gardener  may 
come  to  naught  by  reason  of  unfavorable  weather  and  bad 
seasons  for  growth.  In  dry  summer  weather,  when  it 
becomes  necessary  to  water  the  garden  and  lawn,  it  is  better 
generally  to  thoroughly  soak  the  portion  where  any  water 
at  all  is  applied,  and  not  to  repeat  until  the  ground  has  again 
become  dry  to  the  depth  of  about  three  inches.  The  deeper 


SURROUNDINGS  OF  THE  HOME  245 

plants  root  the  less  likely  they  are  to  die  in  dry  weather. 
Frequent  sprinklings  in  place  of  a  thorough  soaking  of  the  soil 
results  in  a  shallow  root  growth. 

The  care  of  a  home  garden  is  an  excellent  preparation  for 
the  college  courses  in  Agriculture  that  have  to  do  with 
man's  part  in  shaping  conditions  so  that  the  earth  "may 
yield  her  increase".  Studies  in  plant  biology,  having  to  do 
with  the  processes  of  plant  growth  and  the  perpetuation  of 
plant  species,  are  made  far  more  profitable  because  of 
knowledge  gained  in  the  care  of  plants  at  home. 

It  is  by  these  labors  in  the  garden,  about  the  home,  and  in  the 
household  that  a  love  for  the  home  place  and  its  surroundings 
is  fostered.  This  is  separate  from  and  yet  very  closely 
associated  with  a  regard  for  those  who  make  up  the  family 
circle.  It  is  these  ties,  wrought  out  perchance  in  weariness 
at  the  time,  which  lead  many  a  man  and  woman  in  the  later 
years  of  life  to  revisit  and  linger  over  the  old  home  scenes. 
Woe  betides  a  nation  whose  young  people  grow  up  and  never 
learn  through  labor  to  make  better  some  place  that  is  to 
them  a  home.  In  the  surroundings  of  garden,  trees,  lawn, 
and  shrubbery,  the  home  owner  may  find  more  of  enjoy- 
ment than  in  any  restless  wanderings  to  and  fro  in  the  world. 
There  is  a  dignity  to  labor,  and  a  strength  in  citizenship, 
closely  associated  with  the  maintenance  of  a  home.  We 
may  well  suppose  that  the  home  of  Longfellow's  Village 
Blacksmith  was  not  far  from  the  shop  where  it  is  said  that  in 
honest  toil 

"He  earns  whate'er  he  can, 
And  looks  the  whole  world  in  the  face, 
For  he  owes  not  any  man." 

John  Howard  Payne's  "Home,  Sweet  Home"  may  well 
be  sung  by  each  succeeding  generation  of  American  citizen- 
ship as  an  expression  of  a  healthy  sentiment  to  cherish. 
Love  of  home  is  a  sure  foundation  for,  if  indeed  it  is  not 


246  GENERAL  SCIENCE 

the  chief  element  in,  a  patriotism  that  knows  no  sacrifice 
too  great  for  the  welfare  and  the  security  of  one's  coun- 
try whether  in  times  of  war  or  of  peace.  No  sentimental 
attachments  for  the  home  of  one's  youth,  however,  should 
prevent  a  person  from  assuming  the  responsibilities  of  citi- 
zenship in  the  new  land  where  he  may  make  his  permanent 
home.  Though  the  land  in  which  one  dwells  be  his  by 
adoption  rather  than  his  " native  land,"  the  ties  that  centre 
in  a  home  as  one  makes  it  for  himself  warrant  the  spirit  if 
not  the  exact  letter  of  Scott's  lines 

"Breathes  there  a  man  with  soul  so  dead, 
Who  never  to  himself  hath  said, 
This  is  my  own,  my  native  land!" 

SUMMARY 

The  home  garden  may  be  made  to  provide  a  most  enjoyable  and 
wholesome  form  of  open-air  exercise.  In  its  care  one  may  have  the 
great  satisfaction  which  comes  from  witnessing  daily  the  results  of  a 
proper  care  of  plants. 

Botany  as  a  study  in  school  will  yield  far  larger  educational  values 
to  those  who  previously  have  had  some  first-hand  acquaintance  with 
plants  such  as  may  be  gained  in  the  care  of  a  garden.  Then,  too,  what 
is  learned  in  school  of  plants,  and  of  the  conditions  for  their  growth, 
may  in  turn  be  tested  out  in  caring  for  the  home  garden. 

The  industry  and  perseverance  necessary  for  success  in  the  care 
of  a  garden,  coupled  with  that  initiative  which  sees  what  is  necessary 
to  be  done  and  which  undertakes  its  accomplishment,  are  the  very 
traits  necessary  to  success  in  all  the  affairs  of  life. 

It  is  a  part  of  the  history  of  every  nation  that  ownership  of  land  in 
connection  with  the  homes  of  its  people,  and  a  cultivation  of  the  soil 
by  its  owners,  fosters  a  better  home  life,  a  more  industrious  citizenship, 
and  a  greater  stability  of  government. 

In  caring  for  a  garden  no  tillage  of  the  soil  should  be  undertaken 
when  the  ground  is  so  wet  as  to  be  sticky.  However,  as  soon  as  possible 
after  a  rain  the  surface  of  the  ground  during  the  growing  season  should 
be  stirred  enough  to  keep  a  layer  of  an  inch  or  so  of  the  top  of  the  soil 
dry  and  loose.  This  prevents  both  the  drying  out  of  water  from  the 
soil  below  and  the  springing  up  of  a  new  crop  of  weeds. 


SURROUNDINGS  OF  THE  HOME  247 

Exercises 

1.  In  what  ways  may  the  care  of  grounds  and  garden  at  home  be  both  a 
rest  and  a  recreation?     What  advantages  has  such  an  occupation  over 
(a)  complete  cessation  from  physical  activities;  (b)  extended  travel   in 
pursuit  of  rest,  recreation,  and  amusement?     Name  some  special  bene- 
fits sought  in  vacation  trips  away  from  home. 

2.  What  school  studies  may  very  profitably  accompany  the  care  of  gardens 
by  boys  and  girls?     What  out-of-door  responsibilities  at  home  other  than 
care  of  the  garden  may  yield  both  pleasure  and  profit? 

3.  Name  various  fruits  that  may  be  grown  about  the  home  with  no  large 
amount  of  care.     Which   in  your  community  yields   the   best    returns 
annually  on  an  average? 

4.  How  may  ignorance,  carelessness,  or  dishonesty  in  the  growth,  harvest, 
and  distribution   of  seeds  affect  both  national  prosperity  and  individual 
welfare?     What  supervision  is  exercised  at  present  so  that  seeds  on  the 
market  shall  prove  true  to  name,  and  possess  high  germinating  power? 

6.  What  meaning  has  the  phrase  "The  dignity  of  labor"? 

6.  What  is  meant  by  initiative  in  any  of  the  affairs  of  life? 

7.  After  an  examination  of  the  Table  on  page  225,  state  the  value  of  garden 
produce  such  as  tomatoes,  onions,  lettuce,  apples,  berries,  etc.,  relative 
to  the  value  of  meat,  eggs,  and  wheat  flour  in  protein  and  in  calories 
of  energy.     Explain  the  importance  of  vegetables  and  of  fruits  as  an 
essential  part  of  our  foods. 

SOIL  CONDITIONS  FOR  PLANT  GROWTH 

Mixed  with  the  large  and  varying  proportions  of  sand, 
gravel,  stones,  clay,  iron  oxide  and  other  more  or  less  soluble 
substances,  there  are  found  in  fertile  soils  small  quantities 
of  soluble  compounds  of  sodium,  potassium,  nitrogen,  phos- 
phorus, and  a  few  other  chemical  elements.  Apart  from  a 
plentiful  supply  of  water,  it  is  the  exhaustion  of  these  last- 
named  smaller  portions  that  changes  fruitful  soils  into  barren 
ones.  In  arid  and  semi-arid  districts  the  soil  may  be  rich 
in  these  soluble  mineral  compounds  accumulated  through  the 
ages,  the  soil  not  having  been  subjected  to  washings  from 
rainfall.  Irrigation  makes  these  regions  highly  fruitful. 

Sandy  soils  are  likely  to  be  more  or  less  barren  wherever 
found  since  soluble  material  is  washed  down  out  of  reach  of 


248 


GENERAL  SCIENCE 


the  roots  of  plants.  Such  soils  are  said  to  "leach,"  and  fer- 
tilizers applied  to  them  do  not  permanently  enrich  them. 
Their  open  porous  state  permits  the  rapid  evaporation  of 
water  from  them,  too,  while  the  access  of  over  much  air  to  the 
roots  of  plants  is  destructive.  On  the  other  hand,  clay  soils 
filled  with  water  may  exclude  air  from  the  roots  so  completely 
that  plants  do  not  thrive.  Illustrations  of  this  may  often 


FIG.  80. — Irrigation  of  trees. 

be  seen  in  the  stunted  growths  on  low  lands -that  have  been 
overflowed,  and  where  water  has  stood  for  some  time  during 
the  growing  season  for  crops. 

Any  consideration  of  the  roots  of  plants,  and  of  the  manner 
of  supply  of  food  material  to  a  plant  by  osmotic  flow  into 
the  roots,  emphasizes  the  necessity  of  a  finely  divided  state 
of  the  soil.  It  should  be  loose  and  friable  enough  for  the 
tender  root  structures  to  penetrate  it  readily  in  all  directions, 
but  at  the  same  time  sufficiently  compact  so  that  the  rootlets 


SURROUNDINGS  OF  THE  HOME  249 

and  root-hairs  are  all  the  while  in  the  closest  contact  with  the 
soil  particles.  They  should  not  be  subjected  to  any  drying 
effect  from  large  air  spaces,  for  osmotic  action  through  and 
into  the  root-hairs  is  harmfully  affected  and  may  be  wholly 
prevented  by  the  drying  of  their  thin  porous  walls.  The 
finer  the  particles  provided  they  remain  apart  from  one 
another,  the  more  surface  there  is  presented  for  an  adhering 
film  of  water,  and  the  larger  the  available  water  content  of 
the  soil  for  the  plant1. 

The  working  of  the  soil  by  use  of  farm  and  garden  imple- 
ments constitutes  tillage.  Its  chief  purposes  are  to  improve 
the  soil  structure,  to  conserve  the  water  content  in  the  soil, 
and  to  destroy  growths  of  weeds.  The  amount  of  water  that 
a  deeply  worked  fine  soil  bed  will  hold  is  astonishing.  For 
clay  soils  when  saturated  it  is  said  to  be  twenty  pounds  or 
more  of  water  per  cubic  foot. 

Wherever  water  is  in  contact  with  a  solid  that  it  wets 
(clings  to),  the  adhesive  force  lifts  the  water  more  and  more 
until  its  weight  (gravity)  counter-balances  this  adhesion. 
This  is  just  as  true  in  soils  as  it  is  in  glass  tubes  of  small  size 
where,  in  the  study  of  Physics,  this  phenomenon  of  capillarity 
is  most  commonly  noted.  It  is  very  commonly  a  matter  of 
concern  for  the  farmer  to  conserve  the  supply  of  water  held 
in  the  soil  so  that  plants  shall  not  suffer  from  lack  of  sufficient 
moisture.  This  is  especially  true  during  the  growing  season 
with  crops  that  permit  tillage.  Repeated  stirrings  of  the 
surface  soil  interferes  with  and  in  a*  measure  prevents  the 
escape  by  evaporation  of  water  that  has  risen  from  below  by 
capillary  action.  This  water  thus  becomes  available  for 

1  A  quantity  of  soil  when  solidified  into  a  cube  having  a  volume  of  one  cubic 
inch  would  have  six  square  inches  of  surface.  If  we  conceive  this  same 
amount  of  soil  as  particles  in  the  form  of  cubes  o.ooi  inch  on  a  side  there  would 
be  1,000,000,000  soil  particles.  The  combined  surface  of  all  these  separate 
particles  would  be  6000  square  inches.  If  the  soil  particles  were  one-tenth 
of  an  inch  in  size  there  would  be  but  sixty  square  inches  of  surface. 


250 


GENERAL  SCIENCE 


FIG.  81. — Nitrogen  cycle  in  the  life  of  an  alfalfa  plant. 


SURROUNDINGS  OF  THE  HOME  251 

plant  growth.  The  need  of  a  dust  mulch  during  the  hot  dry 
weather  of  summer  is  especially  true  with  gardens  where  the 
soil  is  likely  to  be  heavy  and  compact,  and  in  semi-arid 
regions  where  the  rainfall  is  normally  deficient. 

Enough  air  must  be  present  in  the  soil  to  favor  the  activity 
of  the  bacteria  concerned  in  decay  of  organic  matter  as 
humus,  and  to  furnish  nitrogen  to  the  bacteria  that  thrive 
upon  the  roots  of  peas,  beans,  clover,  alfalfa  and  other  leg- 
umes. Although  nitrogen  as  a  chemical  element  is  essential 
to  plant  growth,  plants  cannot  appropriate  it  as  an  element 
directly  from  the  air.  It  must  be  in  the  form  of  nitrates  or 
other  nitrogen  compounds,  and  these  must  be  dissolved  in  the 
soil  water.  The  "  nitrogen-fixing  "  bacteria  as  a  lower  form 
of  plant  life  are  active  agents  in  maintaining  the.  fertility  of 
soils.  They  are  an  agency  in  the  preparation  of  food  material 
for  the  more  highly  developed  forms  of  plants,  even  as  these 
higher  plants  in  their  turn  prepare  food  for  animals.  The 
soil,  then,  is  not  to  be  looked  upon  as  dead  lifeless  material, 
but  as  filled  with  life  and  activity.  Nitrogen  compounds 
suitable  for  fertilizing  soils  are  now  prepared  in  several  of 
the  countries  of  Europe  direct  from  the  atmosphere  by  means 
of  electrical  discharges  in  a  series  of  chambers  through  which 
an  air  current  is  kept  moving.  Congress  has  authorized 
(1916)  the  establishment  of  a  great  electrical  plant  in  the 
United  States  for  the  production  of  nitrogen  compounds  from 
atmospheric  nitrogen  for  use  in  explosives  and  for  agricultural 
needs. 

So  important  is  a  proper  preparation  of  the  soil  before 
seeding  or  planting  that  any  amount  of  later  cultivation 
during  the  season  cannot  make  good  an  early  neglect..  What 
the  particular  preparation  shall  be  for  any  piece  of  ground 
will,  of  course,  depend  much  upon  the  soil.  College  courses 
in  soils  and  in  cereal  crops  will  fail  to  bring  success  to  any 
farmer  who  does  not  exercise  the  best  of  judgment  in  fitting 


252 


GENERAL  SCIENCE 


his  procedure  to  the  ever-varying  conditions  of  the  weather. 
In  all  agricultural  pursuits,  as  in  business  and  professional 
life,  success  waits  upon  those  who  have  learned  what  ]to  do, 
how  to  do  it,  and  when  it  should  be  done.  And  then  there  is 
always  the  further  requirement  that  any  enterprises  under- 


FIG.  82. — A  good  seed  bed. 

taken  shall  be  carried  through  to  an  end.  School  training 
for  the  farmer  as  for  the  artisan,  the  person  in  business  and 
professional  life,  the  housewife  or  anyone  else,  involves 
discrimination  in  judgment  and  persistence  of  effort  as  well 
as  enlightenment  in  the  realm  of  knowledge.  The  successful 
farmer  must  adapt  the  course  to  be  pursued  day  by  day  in 
farm  operations  to  changing  conditions  of  soils  and  of^crops. 
He  must  take  into  account  the  varying  needs  of  the  farm, 


SURROUNDINGS  OF  THE  HOME  253 

and  exercise  his  judgment  just  as  does  the  business  or  profes- 
sional man  when  called  upon  to  decide  what,  in  mew  of  all 
known  conditions,  is  a  wise  course  to  pursue.  The  farmer 
who  wrests  from  the  soil  an  ample  return  for  the  capital 
invested  and  the  labor  involved,  and  who  lives  comfortably 
all  the  time,  must  be  both  capable  and  efficient.  An  unwise 
course  in  the  care  of  the  soil,  whether  from  ignorance  or  from 
shiftlessness,  invites  failure.  To  achieve  success, here  or  else- 
where man  must  work  harmoniously  with  the  forces  of  nature. 

SUMMARY 

The  fruitfulness  of  soils  that  are  plentifully  watered  is  modified 
greatly  by  their  texture.  There  should  be  sufficient  compactness  to 
prevent  the  leaching  away  of  the  soluble  compounds  essential  to  plant 
growth.  At  the  same  time  there  should  be  no  large  air  spaces  to  allow 
a  rapid  drying  out  of  soil  water,  and  a  destruction  of  the  rootlets  and 
root-hairs.  Then,  too,  the  soil  must  not  be  so  compact  or  so  water- 
soaked  as  to  harm  vegetation  because  of  lack  of  soil  air. 

Tillage  of  the  soil  seeks  to  maintain  a  loose  finely  divided  condition 
favorable  to  the  growth  of  roots  through  it.  If  the  soil  is  too  loose, 
it  must  be  made  more  compact  by  use  of  heavy  rollers  in  order  to  close 
up  the  large  air  spaces.  The  addition  of  much  finely  divided  well- 
rotted  fertilizer  from  the  barn  yard  and  compost  heap,  furnishes 
abundant  raw  material  for  the  growth  of  plants,  and  aids  in  securing 
a  soil  texture  that  is  desirable. 

The  surface  of  the  ground  is  always  to  be  kept  loose  and  dry  so  far 
as  necessary  to  conserve  the  supply  of  water  in  the  soil,  and  should 
be  kept  free  of  weeds.  Care  must  be.  exercised  in  the  cultivation  of 
crops,  not  to  break  off  or  to  destroy  root  systems  already  formed. 
This  would  leave  the  plants  deprived  of  water,  and  starved  for  lack  of 
the  food  material  that  the  injured  roots  have  been  furnishing. 

The  finer  the  soil  particles  the  more  of  them  in  a  cubic  inch,  or  cubic 
foot,  and  the  far  greater  combined  surface  area  to  which  a  film  of  water 
may  adhere.  It  is  from  this  film  of  water  rather  than  from  water 
filling  the  spaces  between  the  soil  particles  that  the  root-hairs  draw 
their  water  supply,  and  upon  it  the  ability  of  plants  to  withstand 
drouth  very  largely  depends. 

Decaying  vegetable  matter  not  only  contributes  toward  making 


254  GENERAL  SCIENCE 

the  soil  friable  and  fine,  but  upon  this  decaying  material  the  "nitrogen- 
fixing"  bacteria  thrive.  Through  their  agency  there  is  left  in  the  soil 
various  soluble  nitrogen  compounds  available  for  use  by  plants. 

While  the  farmer  and  gardener  may  not  be  able  to  make  the  soils 
of  their  lands  just  what  they  may  desire,  it  is  always  possible  to  so 
cultivate  and  fertilize  most  soils  that  if  well  watered  they  will  yield 
good  returns  for  the  labor  put  upon  them. 

Exercises 

1.  For  what  several  purposes  is  soil  plowed?     To  about  what  depth?     Why 
may  fall  plowing  be  somewhat  deeper  than  spring  plowing? 

2.  Aside  from  an  unsightly  appearance,  what  two  serious  objections  are 

there  to  allowing  growths  of  weeds  among  crops? 

3.  What  is  meant  by  a  mulch  for  soil,  and  what  is  its  purpose? 

4.  What  characterizes  the  so-called  "dry  farming"  of  the  semi-arid  regions? 
6.  Account  for  the  yellow,  brown,  and  red  colorings  of  clay  banks.     What 

commonly  gives  the  black  color  to  soils? 

6.  What  is  true  of  the  relative  rate  of  decay  of  organic  matter  in  soils  open 
and  porous,  and  in  compact  water-soaked  soils?     Why  so? 

7.  By  what  means  is  nitrogen  that  is  in  a  free  state  in  the  air  within  the  soil 
converted  into  compounds  suited  for  plant  food?     In  what  way  does  the 
free  oxygen  of  the  air  get  into  plants? 

8.  What  is  the  especial  function  of  the  root-hairs  of  plants?     Explain  the 

effect  on  many  plants  of  having  the  spaces  of  the  soil  filled  with  water. 
Name  any  plants  that  grow  in  (and  under)  water. 

9.  What  is  (a)  humus;  (b)  silt? 

10.  By  calculation  fill  out  the  following  table  showing  the  amount  of  surface 
in  one  cubic  inch  volume  when  subdivided  smaller  and  smaller.  (Cubes 
are  used  for  ease  in  calculation.) 

Side  of  cube i  inch  o.iinch          o.oi  inch          o.ooi  inch 

Number  of  cubes i  1000  

Amount  of  surface 6  sq.  in.          60  sq.  in.         

TREE  PLANTING 

A  deplorable  waste  of  natural  resources  in  the  United 
States  has  taken  place  in  a  wholesale  wanton  destruction  of 
the  forests.  Succeeding  generations  will  long  mourn  these 
unchecked  practices  as  an  enormous  economic  loss  both  direct 
and  indirect.  Millions  of  acres,  unfit  for  any  use  other  than 
timber  growing,  have  been  so  devastated  that  instead  of 


SURROUNDINGS  OF  THE  HOME  255 

furnishing  successive  crops  of  wood  and  lumber  for  all  time 
to  come  they  are  left  treeless,  and  their  soil  as  the  product 
of  ages  of  rock  disintegration  has  been  gullied  and  washed 
away  from  their  rugged  slopes.  The  United  States  Govern- 
ment through  its  Forest  Service  is  doing  something  toward 
reforesting  certain  areas,  and  more  especially  toward 
conserving  the  timber  supply  still  standing.  The  most 
hopeful  outlook  is  in  those  areas  where  new  growths  have 
sprung  up  on  lands  less  despoiled  by  the  erosion  that  so 


FIG.  83. — Ways  of  modern  lumbering. 

often  has  followed  wholesale  timber  butchery.  But  re- 
forestation is  expensive  at  the  best,  both  in  outlay  for  labor 
and  in  the  long  period  of  years  before  the  new  growths  are 
large  enough  for  market.  So  slow  of  growth  are  certain 
trees  that  it  is  practically  impossible  to  reforest  with  them. 
Under  wise  management  it  is  possible  to  get  from  forest 
lands  a  large  annual  return  in  wood  and  lumber,  and  to 
maintain  at  all  times  an  undiminished  vigorous  growth  of 
timber. 

Forest  fires  cause  serious  annual  losses  in  the  timber  supply 
of  the  country  yet  remaining.  It  has  been  estimated  that 
they  have  destroyed  fifty  million  dollars  worth  of  timber 


256  GENERAL  SCIENCE 

annually  for  the  last  forty  years.  They  are  commonly  the 
result  of  carelessness  and  indifference  on  the  part  of  those 
who  camp  in  the  woods,  and  who  fail  to  take  necessary  and 
reasonable  precautions  against  fires.  These  forest  fires  not 
only  damage  and  destroy  matured  timber,  but  they  destroy 
the  young  growths  and  seedlings,  together  with  the  seed- 
bed of  rich  decaying  vegetable  matter  and  its  store  of  seeds 
which  have  not  yet  germinated. 

So  expensive  has  lumber  already  become  that  large  use  is 
now  made  of  iron,  concrete,  cement,  and  brick  in  all  kinds 
of  structural  work.  The  outlay  for  the  single  item  of  pack- 
ing-boxes alone  aggregates  annually  large  sums  in  trade  and 
commerce,  and  merchandise  is  more  and  more  being  packed 
for  shipment  in  paper,  heavy  cardboard,  fibre,  metal,  and 
other  wrappings.  Such  charges  as  these  over  what  was 
necessary  when  there  was  an  abundance  of  cheap  lumber 
is  one  of  the  items  in  an  increased  cost  of  living.  The  small 
home  owner  finds  in  the  high  prices  of  lumber  an  outlay  that 
proves  a  serious  handicap  in  buying  and  paying  for  a  house 
and  its  furnishings.  Directly  and  indirectly  as  the  natural 
resources  of  a  country  are  reduced,  and  their  cost  price 
advances,  those  who  pay  these  larger  prices  out  of  the  wages 
received  for  their  labor,  whether  skilled  or  unskilled,  are 
more  and  more  at  a  disadvantage,  especially  where  there  is 
but  small  advance  in  wages  received. 

One  direct  result  of  a  widespread  education,  and  of  an 
enlightenment  of  the  people  that  keeps  pace  with  advances 
in  human  knowledge  and  with  man's  mastery  over  the  forces 
of  nature,  should  be  the  husbanding  of  the  resources  a  nation 
possesses,  and  an  increase  in  this  store  of  possessions.  It  is 
not  only  well  to  make  "two  blades  of  grass  grow  where 
there  was  but  one  before,"  but  two  trees  should  take  the 
place  of  one  in  the  country  at  large  and  two  bushels  of  wheat 
grown  in  place  of  one. 


SURROUNDINGS  OF  THE  HOME  257 

Scientific  forestry  like  scientific  farming  requires  an  en- 
lightened citizenship  to  apply  the  principles  and  follow  the 
procedure  that  attends  upon  the  advances  of  science  in  this 
field  of  human  effort.  It  requires  the  application  of  business 
methods  where  before  a  reckless  and  haphazard  course  has 
caused  waste  and  destruction,  and  it  involves  consideration 
for  the  welfare  of  the  country  in  the  years  to  come.  The 
"science"  taught  in  schools  fails  in  many  of  its  possi- 
bilities in  education  for  citizenship  where  there  is  failure 
on  the  part  of  those  who  are  taught  to  make  use  of 
the  knowledge  they  have  gained  for  the  benefit  of  the 
community. 

The  actual  planting  of  trees  by  the  average  householder  is 
usually  confined  to  a  few  shade  trees  along  the  street  front  of 
his  home  and  to  some  fruit  trees  at  the  rear  of  the  house.  In 
the  crowded  limits  of  dwellers  in  large  cities  even  this  is 
impossible.  In  the  rural  districts  there  are  ample  oppor- 
tunities for  the  planting  and  proper  care  of  both  shade  and 
fruit  trees.  Such  work  is,  however,  often  poorly  done  or  is 
neglected  altogether.  Some  one  has  estimated  that  a  shade 
tree  in  front  of  a  home,  if  vigorous  and  healthy,  adds  to  the 
valuation  of  a  lot  in  any  town  or  small  city  as  many  dollars 
as  there  are  square  inches  in  its  cross-section  near  the  ground. 
If  its  diameter  is  fourteen  inches,  its  value  in  the  sale  of  the 
property  might  be  reckoned  as  $irr2  =  $3/^X7X7, 
or  $154.  Some  trees  about  a  home  are  so  located,  and  add 
so  greatly  to  the  beauty  and  comfort  of  the  place,  as  to  be 
priceless  to  the  appreciative  owner  and  to  the  passing  public. 
The  man  who  sees  in  trees  about  the  home,  or  standing  out 
prominently  in  the  landscape,  only  so  many  cords  of  wood 
has  missed  something  of  the  best  in  an  education. 

Perhaps  in  tree-planting  better  than  in  some  of  the  simpler 
affairs  of  life  there  is  an  exemplification  of  the  adage  that 
"what  is  worth  doing  at  all  is  worth  doing  well."  Shiftless, 


258  GENERAL  SCIENCE 

unintelligent  ways  of  planting,  and  an  unwise  choice  of  trees 
to  plant,  result  in  unsightly  growths  of  short-lived  trees  which 
are  all  too  often  worthless  for  the  purposes  in  mind  when  set 
out.  The  same  amount  of  effort  well-directed  might  have 
given  long-lived  trees  that  in  beauty  and  service  would  have 
been  to  all  beholders  a  joy  for  generations.  There  is  an 
almost  irreparable  loss  in  those  years  of  growth  that  have 
been  to  little  if  any  purpose. 

So  many  are  the  years  represented  in  the  growth  of  a  fine 
tree  that  it  is  almost  unpardonable  to  harm  it  by  mutilating 
its  top,  by  cutting  off  any  great  limbs,  or  by  injuring  its 
protective  covering  of  bark.  As  a  home  for  the  birds,  as  a 
grateful  shade  for  the  traveler,  and  as  a  source  of  joy  to  every 
passer-by  because  of  the  beauty  they  lend  to  the  landscape, 
it  is  no  wonder  that  trees  figure  so  largely  in  poetry,  painting, 
and  song,  as  well  as  in  the  applied  side  of  life's  activities. 
And  it  is  to  be  remembered  that  all  these  blessings  to  man- 
kind that  cluster  in  trees  belong  to  the  passer-by  as  well  as 
to  him  who  owns  the  title  deed  to  the  ground  in  which  they 
grow. 

SUMMARY 

Scientific  forestry  removes  from  wooded  lands  from  time  to  time 
only  certain  portions  of  the  timber  for  lumber,  wood  pulp,  fuel,  etc. 
It  seeks  to  maintain  continuously  a  sufficient  growth  of  young  and  vig- 
orous trees. 

There  are  large  areas  in  different  portions  of  the  United  States  where 
the  land  is  unfit  for  tillage,  but  is  admirably  suited  for  timber  growing. 
When  the  timber  is  taken  from  steep  slopes  care  should  be  taken  not 
to  destroy  the  undergrowth,  and  not  to  allow  erosion  of  the  soil. 

Forest  fires  not  only  destroy  the  value  of  standing  timber  but  by 
burning  the  seedlings,  and  the  decaying  vegetation  Which  forms  a  rich 
seed-bed  on  the  surface  of  the  ground,  later  forest  growths  are  made 
improbable. 

The  national  government  is  setting  aside  large  tracts  about  the 


SURROUNDINGS  OF  THE  HOME  259 

head  waters  of  navigable  streams  in  order  to  regulate  their  seasonal 
flow  .as  well  as  to  preserve  the  natural  beauties  of  those  regions. 

Shade  trees  along  highways  and  about  homes  add  to  the  beauty  and 
comfort  of  life.  A  wise  choice  should  be  made  of  the  kind  of  trees 
set  out,  and  the  best  of  care  and  judgment  should  be  exercised  in 
transplanting  them  in  order  to  avoid  disappointment  in  results. 

When  trees  are  uprooted  for  transplanting,  the  smaller  roots  and  the 
rootlets  are  largely  left  in  the  ground.  It  is  through  the  rootlets  that 
the  needed  soil  water  is  taken  into  a  growing  tree.  By  exposure  to 
sunlight  and  air  the  root  surfaces  become  dry  and  less  fit  to  take  up 
moisture  from  the  ground  when  again  set  out.  For  these  reasons  the 
top  of  a  newly  set  tree  must  be  nearly  all  cut  off.  The  escape  of  water 
from  too  many  leaves,  and  at  a  rate  faster  than  the  roots  at  first  can 
supply  it,  kills  the  tree  before  it  has  had  time  to  develop  new  roots. 

Exercises 

1.  What  are  some  desirable  shrubs  to  plant  in  front  yards? 

2.  Discuss  in  detail  the  steps  and  precautions  to  be  taken  in  transplanting 
shrubs  and  trees. 

3.  Name  two  of  the  common  shade  trees  of  your  community,  and  give  the 
characteristics  whereby  you  distinguish  them  at  sight. 

4.  Make  a  list  of  all  the  ornamental  trees  and  shrubs  of  your  neighborhood 
known  to  you  by  sight,  not  including  any  which  would  be  classed  as 
shade  trees  when  grown. 

TREES  OF  THE  NEIGHBORHOOD 

We  recognize  our  friends  at  sight.  Chance  acquaintances 
we  may  come  to  call  by  name.  In  neither  case,  however, 
is  it  commonly  true  that  we  could  give  descriptions  of  them 
sufficiently  definite  to  insure  their  identification  by  others. 

Description  of  trees  in  books,  if  of  very  much  use  as  a 
guide  in  learning  to  know  them  at  sight,  presupposes  con- 
siderable first-hand  knowledge  of  the  trees  round  about  us. 

Where  any  one  kind  of  tree  is  known  by  name,  and  repeated 
notice  is  taken  of  it,  there  comes  not  only  a  more  extended  but 
a  more  detailed  knowledge  of  its  characteristics.  By  con- 
trasting its  features  with  the  corresponding  ones  of  other 
trees  whose  names  have  been  learned,  there  comes  about  in 


260 


GENERAL  SCIENCE 


time  an  acquaintanceship  with  trees  similar  to  that  which 
we  have  with  persons. 


FIG.  84. — An  American  elm  in  winter. 

One  of  life's  greatest  sources  of  pleasure,  and  one  of  its 
privileges,  is  to  have  " speaking  acquaintance"  with  every 


SURROUNDINGS  OF  THE  HOME  261 

tree,  shrub,  herb,  and  weed  met  in  one's  daily  walks.  Recog- 
nition of  new  plants  as  members  of  a  well-known  family  is 
much  the  same  as  to  learn  that  a  chance  acquaintance  is  a 
relative  of  some  friend  of  ours. 

In  order  to  describe  trees  for  purposes  of  identification 
it  is  well  to  make  use  of  some  technical  terms  of  definite 
meaning.  All  who  would  have  any  complete  knowledge  of 
plants  must  study  Botany.  But  it  is  not  necessary  to  be  a 
botanist  in  order  to  know  and  appreciate  trees,  any  more  than 
it  is  necessary  to  be  a  psychologist  in  order  to  know  and  love 
our  friends.  It  is  probable,  however,  that  one  who  comes  to 
know  trees,  and  to  understand  something  of  the  conditions 
for  their  growth  and  well-being,  will  desire  to  have  a  knowl- 
edge of  Botany.  Studies  of  the  plants  with  which  one  is 
more  or  less  familiar  may  prove  an  excellent  introduction  to 
it. 

The  general  form  of  trees  taken  as  a  whole  is  one  of 
their  distinguishing  characteristics.  An  observer  who  is  ac- 
quainted with  trees  readily  recognizes  any  familiar  kind  by  its 
form  even  at  a  distance.  Yet  to  describe  just  what  is 
meant  by  the  "form"  of  any  tree  is  not  easy.  For  one  thing 
trees  are  classed  as  having  tops  spreading  (as  the  apple  and 
white  elm),  or  erect  (as  evergreens  and  poplars).  The  angle 
which  the  branches  make  with  the  tree  trunk  is  in  a  general 
way  a  noticeable  feature;  so  is  the  relative  amount  of 
smaller  branches  and  twigs  (the  "spray"). 

To  one  well  acquainted  with  trees  the  appearance  of  the 
bark  on  the  trunk  and  on  the  younger  growths  of  limbs 
identifies  the  kind  of  tree.  The  beginner  must  acquire  this 
ability  of  recognition  through  personal  acquaintance  with 
different  trees,  getting  it  incidentally  in  connection  with  other 
means  of  identifying  them.  As  trees  grow  the  old  bark 
cracks  in  a  variety  of  ways  often  characteristic  of  the  kind 
of  tree,  and  as  new  bark  forms  underneath  year  by  year  these 


262  GENERAL  SCIENCE 

ridges  of  older  bark  are  gradually  pushed  outward.  The 
bark  grows  more  and  more  rough,  and  in  some  trees  drops 
off  (is  " flaky").  In  some  trees  (as  birch  and  cherry)  the 
bark  remains  smooth  and  noticeably  marked  by  horizontal 
streaks.  These  result  from  the  stretching  of  the  bark  due  to 
growth  within,  and  a  consequent  change  of  form  in  the 
lenticels  or  breathing  pores  of  the  bark.  Some  inner  barks 
have  characteristic  tastes  readily  identifying  such  trees  as 
the  sassafras,  slippery  elm,  birch,  cherry,  and  some  oaks. 
A  characteristic  general  color  or  tone  of  the  outer  bark  as  a 
whole  is  an  aid  in  distinguishing  trees.  In  this  latter  case 
there  is  a  difference  between  their  appearance  in  summer  and 
in  winter. 

The  leaf  scars  upon  the  twigs  and  smaller  branches  may  be 
opposite  each  other  at  the  same  node  (place  where  one  or 
more  leaves  grow),  or  they  may  be  alternate,  with  one  leaf 
scar  only  at  a  node.  These  latter  are  arranged  lengthwise  of 
the  stem  in  rows  of  two  or  more,  and  the  number  of  these 
rows  should  be  determined. 

The  presence  or  absence  of  a  terminal  bud  on  the  twig  is  to 
be  noted,  together  with  the  general  form  of  the  buds  and  any 
general  characteristics  in  their  color,  odor,  and  any  protective 
coverings  such  as  hairs,  gum,  or  down. 

The  fruits  of  the  tree  in  season  serve  to  identify  it,  and  so 
do  the  flowers.  Good  cuts  in  books  aid  materially  in  studies 
such  as  these.  While  by  use  of  a  reliable  and  complete 
"key"  one  may  become  fully  assured  of  the  identification 
of  any  tree,  it  must  always  be  kept  in  mind  that  an  acquaint- 
anceship with  trees  to  be  a  source  of  real  enjoyment  must 
at  first  be  personal  and  not  bookish.  The  use  of  a  book  in 
tree  studies  is  like  the  use  of  a  guide  book  in  one's  travels, 
telling  what  to  look  for  and  its  striking  characteristics  but 
never  taking  the  place  of  actual  and  personal  inspection  of 
what  is  described. 


SURROUNDINGS  OF  THE  HOME  263 

SUMMARY 

Any  knowledge  of  trees  to  be  satisfactory  and  complete  must  be 
gained  by  personal  acquaintance  with  them.  The  use  of  a  "key"  for 
their  identification  presupposes  some  knowledge  of  trees,  and  is  not 
a  substitute  for  first-hand  studies  of  them. 

A  "key"  tells  what  to  look  for,  and  how  quickly  and  sharply  to  differ- 
entiate between  characteristics  of  trees  that  are  alike  in  many  respects. 
Good  pictures  of  trees,  their  leaves,  flowers,  and  fruits,  are  a  great  aid 
in  their  identification  when  met  in  woodland,  roadside,  and  nursery. 

School  studies  of  the  leaves,  buds,  flowers,  manner  of  branching, 
kind  of  bark,  etc.,  of  some  few  trees  make  possible  the  recognition  of 
other  trees  whose  characteristics  are  noted  as  different  from  those 
studied. 

Shrubs,  evergreens,  and  ornamental  trees  on  lawns  and  in  parks 
should  be  included  in  any  list  of  tree  acquaintances. 

SOME  PLANT  STUDIES 

Any  knowledge  of  the  common  plants  of  garden  and  farm 
and  roadside,  though  it  be  of  the  most  general  nature,  makes 
apparent  the  fact  that  their  parts  include  roots,  stem  (trunk 
and  branches),  leaves,  and  flowers.  So  far  as  the  plant 
economy  is  concerned  flowers  and  fruit  have  for  an  immediate 
end  the  maintenance  of  the  species  so  that  plants  shall  not 
become  extinct.  The  root,  stem,  and  leaf  are  directly  con- 
cerned in  the  growth  and  nourishment  of  the  living  plant. 
It  may  be  considered  that  the  chief  purpose  of  the  stem  of  the 
plant  whether  of  the  largest  tree  or  the  most  insignificant 
weed  of  the  field,  is  to  secure  the  largest  'exposure  of  leaf 
surface  to  air  and  sunlight.  The  stem  of  a  leaf  (petiole), 
and  its  framework  of  midrib  and  veins,  serves  a  like  purpose. 

To  the  botanist  the  leaves  of  a  plant  are  so  many  labora- 
tories, and  to  the  economist  so  many  factories,  whence  comes 
the  food  supply  of  mankind.  All  things  we  eat  come  from 
plants.  Just  how  this  is  accomplished  is  discussed  in  another 
lesson.  Plants  alone  can  take  as  raw  materials  carbon  di- 
oxide gas  from  the  air,  and  soil  water  which  has  in  it  in  solu- 


264 


GENERAL  SCIENCE 


tion  minerals  and  nitrogen  compounds,  and  convert  these 
into  food  for  animals  and  for  sustaining  the  life   of   the 


FIG.  85. — Structure  of  the  dandelion. 


plant  itself.     As  stored  in  fruits,  seeds,  and  roots,  this  food 
supply  is  primarily  for  a  later  generation  of  young  plants. 


SURROUNDINGS  OF  THE  HOME  265 

While  it  is  chiefly  in  the  leaves  that  this  food  production 
occurs,  in  a  lesser  degree  it  is  carried  on  in  all  the  green  parts 
of  a  plant.  The  energies  of  plants  of  the  higher  order  seem 
to  be  directed  toward '  maturing  seeds  for  the  succeeding 
generations  of  their  own  kind.  Wherever  seeds  occur  there 
must  have  been  flowers.  These  flowers  may  have  been  desti- 
tute of.  the  showy  petals  we  so  commonly  associate  with  the 
thoughts  of  flowers,  and  some  one  or  more  of  the  other  parts 
of  a  complete  flower  may  be  lacking.  Indeed,  the  study  of 
Botany  has  very  much  to  do  with  plants  that  never  have 
flowers.  Many  of  these  non-flowering  plants  are  of  micro- 
scopic size,  and  propagate  themselves  in  ways  other  than  by 
seeds. 

Nature's  provision  for  the  scattering  of  seeds,  and  for 
their  protection  till  conditions  favorable  for  growth  occur, 
is  an  interesting  chapter  in  Botany.  The  fleshy  fruits  for 
example  are  gathered  as  food  by  man,  birds,  and  other  ani- 
mals, and  their  seeds  become  widely  scattered.  Many  seeds 
are  carried  long  distances  by  winds  and  streams.  Where 
seeds  become  so  thickly  scattered  that  upon  germination 
the  young  plants  are  over-crowded,  only  the  most  vigorous 
of  the  young  plants  survive  in  the  struggle  for  existence. 
The  others  will  be  choked  and  starved  out,  an  example  of  the 
" survival  of  the  fittest"  in  the  natural  world. 

The  process  of  fertilization  of  the  ovules  of  a  flower  so  that 
they  become  seeds  which  will  "grow"  introduces  us  to  botan- 
ical terms  that  are  best  learned  in  connection  with  the  study 
of  some  flower  in  the  laboratory.  The  pollen'  when  ripened 
is  shed  from  the  anther  in  which  it  grew.  These  anthers  are 
at  the  outer  extremities  of  the  stamens.  The  pollen  grains 
as  carried  by  winds,  bees,  and  insects  generally,  may  fall 
upon  the  stigma  of  a  pistil  in  some  flower  of  the  same  kind  of 
plant.  Their  growth  down  through  the  style  into  the  ovules 
accomplishes  the  fertilization  necessary  for  the  develop- 


266  -  GENERAL  SCIENCE 

ment  of  the  ovules  into  seeds.  In  due  time  the  enlarged 
ovary  becomes  the  ripened  fruit,  and  the  ovules  ripened 
seeds.  The  ovary  wall  itself  may  become  juicy  as  in  the 
currant,  grape,  and  tomato,  or  it  may  become  a  shell  as  in 
the  walnut. 

In  many  plants  all  these  acts  of  fertilization  occur  within  a 
single  flower;  in  others  the  pistillate  and  staminate  flowers 
occur  in  different  parts  of  the  same  plant,  and  sometimes 
they  are  borne  on  entirely  different  plants. 

The  petals  taken  together  form  the  corolla  whose  bright 
colors  in  many  flowers  undoubtedly  attract  insects  as  agents 
in  pollination.  The  small  green  sepals  forming  the  calyx 
serve  in  the  bud  of  the  unopened  flower  to  protect  the  en- 
closed parts  from  cold  and  wet  and  from  insect  enemies. 
In  the  process  of  the  development  of  the  flower  the  calyx 
may  become  greatly  modified,  even  into  such  structures  as 
the  pulp  of  the  apple  and  pear. 

It  is  to  be  kept  in  mind  in  all  studies  of  flowers,  and  of 
plants  in  general,  that  variation  rather  than  uniformity  is 
the  rule.  Any  extended  study  of  flowers  and  plants  from 
the  specimens  themselves  soon  reveals  the  fact  that  the 
adaptability  of  plants  to  varying  conditions  affecting  their 
lives  is  one  of  the  wonderful  features  of  plant  development. 

Many  plants  that  bear  seeds  are  independent  of  these  seeds 
for  their  propagation.  Each  generation  may  provide  for 
new  plants  by  the  growth  of  creeping  stems  or  "  runners" 
as  in  the  strawberry,  or  by  bulbs  as  in  the  onion,  lily  and 
tulip,  or  by  underground  stems  as  in  the  hop  plant  and  the 
common  potato.  Seedless  oranges  are  secured  by  grafting 
into  small  orange  trees  of  the  common  sort  twigs  that 
have  been  cut  from  an  orange  tree  whose  fruit  persistently 
fails  to  develop  seeds.  Bananas  are  raised  from  sprouts  aris- 
ing from  the  old  roots.  Florists  and  nursery  men  use  short 
lengths  of  the  stems  of  some  plants,  such  as  the  geranium, 


SURROUNDINGS  OF  THE  HOME  267 

currant,  and  grape  to  start  new  plants,  by  bedding  the  lower 
ends  of  these  " cuttings"  in  moist  earth  till  they  develop 
roots. 

SUMMARY 

The  root,  stem,  and  leaf  are  the  parts  of  a  plant  directly  concerned 
in  its  nourishment  and  perfection.  Its  buds,  flowers,  and  fruit  are  for 
the  purpose  of  continuing  the  species. 

The  roots  hold  the  plant  firmly  in  place  in  the  soil.  Through  them 
comes  the  water,  and  the  minerals  held  in  solution  by  the  water,  out  of 
which  in  part  the  plant  manufactures  material  for  its  own  growth, 
and  food  for  man  and  other  animals. 

Through  the  leaves  the  plant  rids  itself  of  surplus  water  from  the 
sap  by  the  process  known  as  transpiration.  From  the  air  through  their 
leaves  plants  get  carbon  dioxide  gas  which  is  the  other  important  raw 
material  for  the  manufacture  of  food  in  plant  growth. 

Only  plants  can  manufacture  starch,  sugar,  oils,  and  proteins  out 
of  water,  carbon  dioxide,  nitrogen  compounds,  and  some  few  other 
substances  taken  from  the  soil.  This  chemical  change  occurs  chiefly 
in  the  leaves  when  exposed  to  sunlight. 

Seeds  and  their  protecting  envelope  constitute  the  fruit  of  the  plant. 
While  many  times  these  fruits  are  edible,  sometimes  seeds  and  all,  in 
other  cases  the  husks,  rind,  or  shell  serves  no  purpose  other  than  as  a 
protection  to  the  seeds.  Tomatoes,  pumpkins,  and  squashes  are  fruits 
by  this  definition  as  much  as  are  cherries,  apples,  and  oranges. 

At  the  inner  end  of  the  style  of  a  pistil  is  the  ovule  which  before  it 
can  develop  into  a  seed  must  be  fertilized.  This  is  accomplished  by  the 
growth  of  a  pollen  grain  from  the  stigma  down  through  the  style  and 
into  the  ovule.  In  many  plants  the  pollen  is  developed  in  the  anthers 
of  stamens  in  the  same  flowers  that  bear  the  pistils,  and  self-fertiliza- 
tion may  take  place.  In  other  cases  the  pollen  comes  from  other 
flowers  on  other  plants  and  cross-fertilization  occurs. 

Many  plants  are  propagated  naturally  by  bulbs,  by  underground 
stems,  by  stems  above  ground  known  as  runners,  or  by  sprouts  arising 
from  buds  developed  around  the  base  of  the  stem  below  ground. 
Plants  are  propagated  artificially  by  grafting,  budding,  and  by  use  of 
cuttings. 

In  studies  of  the  same  kind  of  plants  it  soon  becomes  apparent  that 
there  are  wide  differences  other  than  of  size.  It  is  also  apparent  that 
plants  adapt  themselves  to  varying  conditions.  Even  the  leaves  on 
the  same  plant  often  show  marked  variations  in  form. 


268  GENERAL  SCIENCE 

USEFULNESS  OF  PLANTS  TO  MAN 

Without  plant  life,  and  its  continuous  consumption  of 
carbon  dioxide  from  the  air,  all  available  carbon  of  the  earth 
in  time  would  be  in  the  atmosphere.  A  corresponding 
amount  of  free  oxygen  would  have  been  taken  from  the 
atmosphere  permanently  to  form  carbon  dioxide.  In  the 
round  or  " cycle"  of  changes  for  the  element  carbon,  plants 
appropriate  solar  energy  as  heat  and  light  from  the  sun  in 
the  chemical  changes  that  occur  in  the  chloroplasts.  This 
energy  in  turn  becomes  available  in  animals  through  oxi- 
dation of  the  carbohydrates  of  the  digested  food.  In  a 
very  real  sense  our  power  to  do  work,  both  physical  and 
mental  (brain  activity),  is  from  liberated  energy  derived  from 
the  sun  and  made  available  to  us  through  the  agency  of 
plants.  Without  plants  all  this  round  of  transformation 
of  energy  would  be  blocked. 

The  yield  of  dry  hay  from  meadow  land  may  be  two  tons 
per  acre.  The  growth  of  corn  stalks  per  acre  when  dried 
may  weigh  two  tons  or  more.  A  large  part  of  the  weight 
of  the  stems  of  grass,  of  wheat  and  other  grains,  of  corn 
stalks,  and  of  the  woody  stems  of  all  shrubs  and  trees,  is  the 
substance  known  as  cellulose  (C6Hi0O5).  Over  40  per  cent 
of  cellulose  is  carbon.  Plants  get  the  food  material  for 
cellulose  in  part  from  the  soil  through  their  roots  in  the  form 
of  water,  but  the  carbon  is  taken  in  by  the  leaves  in  the 
form  of  carbon  dioxide  gas.  A  yield  of  fifty  bushels  of 
shelled  corn  per  acre  represents  a  weight  of  nearly  one  and 
one-half  tons  of  the  grain.  Of  this  nearly  one-half  (45  per 
cent)  is  carbon.  When  the  amount  of  carbon  gathered  in 
from  the  atmosphere  by  the  growth  of  vegetation  during  a 
season  is  estimated  in  tons  per  acre,  the  importance  of  this  one 
function  of  the  leaves  and  of  the  green  parts  of  the  stems  of 
plants  becomes  apparent.  In  the  chloroplasts,  under  the 


SURROUNDINGS  OF  THE  HOME 


269 


TREE  INCREASES  EACH 
YEAR   IN  HEIGHT  AND 
SPREAD  OF  BRANCHES 
BY  ADDING  NEW  GROWT 

OF  TWIGS. 


INNER  BARK  CARRIES 

PREPARED  FOOD  FROM 
LEAVES   TO  CAMBIUM 


AlR  SUPPLIES  CARBON.  THE    PRINCIPAL 
FOOD  OF  THE   TREE.  TAKEN  IN  ON 
UNDER  SURFACE  OF  LEAVES. 

LEAVES  PREPARE  THE  FOOD 
OBTAINED   FROM  AIR  AND 
SOIL  AND  GJVE'OFF 

MOISTURE. 
,  BY   TRANS^ 

PIRA~%j£  LIGHT  AND  HEAT 

ION .^5*  NECESSARY  FOR 
CHEMICAL 
CHANGES 


HEARTWOOD  (INACTIVE) 
GIVES  STRENGTH 


THE  BREATHING  PORES  OF" 
THE  ENTIRE  TREE  ;ON  LEAVES, 
TWIGS.BRANCHES,  TRUNK  AND 

ROOTS, TAKE  IN  OXYGEN. 

FLOODING. POISONOUS  GASES 

OR"  SMOKE    MAY  KILL  A  TREE  . 


SAPWOOD  CARRIES  SAP 
FROM  ROOTS  TO  LEAVES 


CAMBIUM  (MICROSCOPIC) 
BUILDS  THE  CELLS 


OUTER  BARK  PROTECTS 
TREE  FROM  INJURY 


SURFACE  ROOTS 


SURFACE: 
ROOTS:  _ 

ROOTS^~ 


:Root  TIPS  OR 

ROOT    HAIRS 
TAKE    UP  WATER 
CONTAINING    SMALL  QUAN- 
TITY  OF  MINERALS    IN    SOLU- 
TION 


FIG.  86. — Structure  of  tree,  and  functions  of  its  parts. 


270  GENERAL  SCIENCE 

influence  of  the  sunlight,  carbon  is  built  into  the  substances 
starch  and  sugar.  These  are  foods  for  the  support  of  plant 
growth  as  well  as  foodstuffs  for  animals.  The  liberated 
oxygen  is  returned  to  the  atmosphere. 

Carbon  dioxide  gas  used  by  plants  in  making  their  food  is 
a  product  of  the  oxidation  of  substances  containing  carbon. 
Its  chief  sources  are  the  respired  air  of  all  forms  of  animal 
life,  the  combustion  of  vegetable  matter  including  coal,  and 
the  decay  of  vegetation.  The  loss  of  the  leaves  of  any 
plant  by  hail  storms,  "  worms,"  or  caterpillars,  deprives 
the  plant  of  power  to  produce  enough  food  for  its  continued 
growth  after  any  stored  supply  has  been  exhausted.  This 
means  a  starved  condition  for  the  plant  that  is  likely  to  kill  it. 

Not  least  of  the  activities  of  the  leaves  of  plants  is  their 
liberation  of  water  which  has  come  up  to  them  from  the 
depths  of  the  soil  through  their  roots.  A  single  thrifty 
sunflower  plant  gives  off  into  the  air  by  transpiration  as 
much  as  a  quart  of  water  per  day.  It  has  been  estimated 
that  a  large  tree  with  abundant  foliage  may  evaporate  through 
its  leaves  several  barrels  of  water  daily  during  the  growing 
season.  From  the  grass  of  lawn  and  field  the  quantity 
evaporated  daily  at  times  during  the  growing  season  may  be 
estimated  as  tons  per  acre.  The  loss  of  water  from  leaves 
as  well  as  the  absorption  of  carbon  dioxide  from  the  air  is 
chiefly  through  the  more  open  cellular  tissue  of  the  under 
sides  of  the  leaves. 

This  would  be  a  strange  world  in  which  to  live  if  there 
were  none  of  the  variety  of  landscape  due  to  plants  of  all 
sorts  and  kinds.  When  to  the  plants  that  are  familiar  to 
us  there  are  added  the  myriad  forms  of  microscopic  size  of 
which  Botany  teaches,  and  when  we  consider  the  usefulness 
of  bacteria  as  man  is  coming  to  know  more  and  more  about 
them,  studies  of  the  plant  kingdom  assume  an  importance 
far  beyond  any  mere  love  of  flowers  for  their  beauty  alone. 


SURROUNDINGS  OF  THE  HOME 


271 


If  a  written  list  is  made  of  fruits  both  domestic  and 
foreign,  whether  recognized  at  sight  or  known  only  by  name, 
and  then  the  names  are  underscored  of  those  of  which  con- 
siderable is  known  and  can  be  told,  a  lack  of  definite  knowl- 
edge of  many  of  them  is  likely  to  become  at  once  apparent. 
If  similar  lists  of  grains,  of  nuts,  and  of  textile  plants  are 
made,  too,  it  serves  as  a  test  of  how  much  we  know  definitely 
about  what  are  commonly  called  the  " useful  plants." 


FIG.  87. — Relative  importance  of  the  leading  crops  of  the  United  States. 

The  cotton  plant  has  long  furnished  to  mankind  inexpen- 
sive and  durable  clothing  easily  adapted  to  a  wide  range  of 
uses.  With  various  chemical  treatments  of  the  cotton  fibre, 
and  the  wonderful  results  achieved  in  dyeing  cotton  fabrics 
in  these  days,  the  products  of  factories  employed  in  convert- 
ing cotton  into  manufactured  forms  amaze  one  in  their 
variety  and  their  attractiveness.  Any  list  of  the  cotton 
goods  manufactured  for  clothing  is  in  itself  highly  suggestive 
of  the  importance  to  mankind  of  this  one  plant.  This  is 
true  not  only  in  the  usefulness  of  its  finished  products,  but 
in  the  employment  furnished  in  the  production  and  manu- 
facture of  cotton,  and  in  the  transportation  of  both  raw 
material  and  manufactured  articles. 


272  GENERAL  SCIENCE 

The  fibre  of  cotton  is  contained  in  the  ripened  seed-pod 
("boll")  of  the  plant.  These  fibres  at  their  inner  ends  are 
attached  to  the  seeds  of  the  plant.  The  invention  of  the 
cotton  gin  by  Eli  Whitney  for  the  successful  separation  of  the 
seeds  from  the  fibre  made  cotton  production  on  a  large  scale 
possible,  and  with  cheap  labor  highly  profitable.  The  rise 
of  slavery  in  the  United  States  as  a  civil  and  political  insti- 
tution accompanied  the  development  of  the  cotton-growing 
industry. 

The  fibre  of  the  flax  plant,  unlike  that  from  cotton,  is 
obtained  from  the  stem.  If  kept  water-soaked  sufficiently 
long,  the  material  between  the  fibres  dissolves  or  rots  away. 
The  fibres  are  then  sorted,  and  the  coarser  ones  are  used  for 
twine.  Others  are  used  for  canvas  and  tent  cloth,  while  the 
finest  of  them  are  used  for  handkerchiefs,  or  in  making 
laces  and  embroideries.  Jute,  hemp,  and  other  like  tropical 
plants  yield  a  coarser  fibre  of  large  usefulness  especially  for 
binding  twine,  rope,  burlap,  matting,  and  the  cheaper  grades 
of  carpet. 

From  the  seeds  of  the  cotton  plant  great  quantities  of 
cotton-seed  oil  are  produced.  This  has  a  large  use  in  soap 
manufacture,  and  in  the  making  of  those  table  products 
which  take  the  place  of  butter  and  lard,  such  as  oleomargarine 
and  cottolene.  It  is  also  used  as  an  adulterant  of  the  more 
expensive  oils,  including  olive  oil  for  table  use.  The  cotton 
seeds  after  the  oil  has  been  pressed  out  of  them  are  ground 
for  cotton-seed  meal  which  is  used  as  a  food  for  cattle.  From 
flaxseed  is  obtained  linseed  oil  widely  used  in  paints.  It 
can  be  readily  spread  by  a  brush  in  a  thin  even  coat  over 
woodwork  and  metal  surfaces.  Upon  exposure  to  the  air, 
and  as  result  of  chemical  changes  that  occur,  it  forms  a 
tough  glossy  waterproof  covering.  This  holds  firmly  within 
it  any  of  the  several  chemical  compounds  used  to  give  "body  " 
to  the  paint,  as  well  as  any  coloring  material  used  for  color 


SURROUNDINGS  OF  THE  HOME  273 

effects.  Lead  carbonate  ("white  lead")  used  with  the  oil 
"  covers  "  well,  i.e.,  it  can  be  applied  as  a  very  thin  coat  of  uni- 
form appearance.  The  thinner  the  paint  coat  the  less  likely  it 
is  to  peel  off.  Zinc  white,  or  zinc  oxide  (ZnO),  as  a  substitute 
for  white  lead  requires  more  oil  for  mixing  and  spreading. 
However,  it  does  not  blacken  so  much  from  the  gases  con- 
taining sulphur  that  are  common  where  soft  coal  is  burned. 
Various  colors  are  given  to  paints  by  mixing  into  them  varying 
proportions  of  different  minerals  as  pigments,  and  these  are 
held  suspended  in  the  oil  as  it  dries.  Black  paint  commonly 
has  lampblack  or  finely  powdered  charcoal  in  it.  Varnish 
is  a  mixture  of  melted  rosin  and  boiling  hot  linseed  oil. 
When  cooled  it  is  thinned  sufficiently  with  turpentine  to  be 
spread  easily  as  a  very  thin  coat  over  woodwork  and  metal 
surfaces.  White  enamel  paint  is  varnish  to  which  white 
lead  has  been  added,  and  various  pigments  added  to  this 
give  rise  to  the  colored  enamel  paints. 

Not  least  among  the  factors  of  modern  life  is  the  daily 
newspaper.  It  is  to  be  noted  in  this  connection  that  print 
and  wrapping  paper  is  largely  if  not  wholly  wood  fibre,  or 
cellulose.  The  wood  is  treated  with  hot  alkaline  liquids  to 
dissolve  out  any  resinous  material  and  to  loosen  the  fibres, 
and  then  rubbed  (" ground")  into  a  pulpy  mass.  This  pulp 
is  bleached  white  by  the  action  of  chemicals,  and  pressed  into 
thick  layers  for  transportation  from  the  mills  to  the  paper 
factories.  A  single  issue  of  a  daily  newspaper  in  one  of  the 
large  cities  may  use  twenty  tons  or  more  of  paper.  Spruce 
is  the  wood  most  desired,  but  pine,  fir,  poplar,  cottonwoods, 
and  many  other  kinds  are  largely  used.  Cotton  and  linen 
rags  are  used  for  the  finer  quality  of  book  and  writing  paper, 
and  straw  for  the  "pasteboard"  used  in  box-making. 

SUMMARY 

From  plants  man  gets  lumber  for  his  dwelling  and  its  furniture, 
cotton  and  linen  fibre  for  his  clothing,  fruits  from  the  orchard,  grain 


274 


GENERAL  SCIENCE 


from  the  fields,  and  vegetables  from  the  garden.  Indirectly  plants 
furnish  him  meat  and  milk  for  food,  and  provide  food  for  the  horse 
that  does  his  work  and  carries  him  to  and  fro  on  business  and  for 
pleasure. 

Without  plants  a  vast  store  of  the  oxygen  of  the  atmosphere  would  in 
time  become  combined  with  the  world's  supply  of  carbon  as  carbon 
dioxide  gas. 

As  result  of  the  storage  by  plants  of  solar  energy  in  the  manufacture 
of  starch,  sugar,  cellulose,  oils,  and  proteins,  the  earth's  supply  of  energy 
to  maintain  life  and  to  do  much  of  its  work  is  continuously  being 
replenished.  The  energy  liberated  in  the  human  body  and  in  animals 


FIG.  88. — The  turpentine  "  orchard  ". 


by  the  process  of  oxidation,  and  in  the  boiler  of  the  steam  engine  when 
coal  is  burned,  is  but  solar  energy  stored  by  plants. 

From  land  surfaces  covered  by  vegetation  there  is  being  given  back 
into  the  air  daily  by  transpiration  of  plants  during  the  growing  season 
amounts  of  water  computed  as  tons  per  acre. 

It  must  not  be  overlooked  in  this  connection  that  paper,  which  in  its 
varied  forms  has  become  so  indispensable  in  modern  life,  is  essentially 
cellulose,  whether  made  from  cotton  or  linen  rags,  from  wood  pulp,  or 
from  straw.  Making  record  of  the  days  happenings  in  newspapers, 
and  of  the  affairs  and  thoughts  of  men  as  set  forth  in  books,  taxes  the 
world's  supply  of  cheap  paper-making  material. 


SURROUNDINGS  OF  THE  HOME  275 

Exercises 

1.  What  is  meant  by  vulcanized  rubber?     What  changes  are  produced  in 
the  rubber  by  vulcanizing  it? 

2.  Describe  how  the  rubber  stamps  in  common  use  are  made? 

3.  To  what  uses  is  old  rubber  put?     Why  has  it  no  greater  market  value? 
About  what  is  the  market  value  of  the  pure  gum  now? 

4.  Read  all  available  material  upon  the  turpentine  industry  of  southeastern 
United  States.     Then  write  a  short  description  of  it,  including  the  care  of 
the  trees,  the  processes  of  manufacture,  the  products  and  their  varied  uses. 

6.  What  are  "mercerized  cotton"  fabrics?     What  especial  advantage  arises 

from  this  treatment? 
6.  Formerly  what  two  plants  furnished  most  of  the  dyes  for  cloth?     How 

were  different  colors  obtained  from  the  same  dye?     At  about  what  date 

were  the  "coal  tar  dyes"  first  produced? 

BIRDS  AROUND  OUR  HOMES 

For  beginners  to  study  birds  from  pictures  and  printed 
descriptions  is  even  more  unsatisfactory  than  it  is  to  study 
trees  from  books  only.  In  making  studies  of  birds  it  is  likely 
that  the  English  sparrow  will  be  at  hand  anywhere.  In 
rural  districts  and  smaller  towns  other  birds  are  likely  to  be 
plentiful.  In  the  zoology  departments  of  some  high  schools 
there  may  be  collections  of  stuffed  birds,  and  mounted  skele- 
tons. The  study  of  certain  of  these  in  detail  may  be  exceed- 
ingly profitable  for  comparisons  of  types  of  bird  life.  Many 
city  parks  have  extensive  aviaries  and  museums.  Any  ex- 
tended study  of  birds  constitutes  a  division  of  Zoology. 
However,  one  need  not  be  a  scientist  in  order  to  have  an 
extended  knowledge  of  the  forms  and  ways  of  birds,  and  to 
enter  into  the  full  enjoyment  of  bird  life. 

Birds  as  distinguished  from  other  animals  are  characterized 
by  a  covering  of  feathers,  and  by  a  modification  of  the  fore- 
limbs  into  wings  that  are  more  or  less  useful  for  flying.  Like 
man  birds  are  bipeds,  and  the  young  experience  difficulty  in 
learning  to  walk  as  well  as  in  becoming  able  to  fly.  For  a 
considerable  time  after  being  hatched  from  the  eggs  young 


276  GENERAL  SCIENCE 

birds  need  to  be  fed  and  brooded  by  the  parents.  Chickens 
and  the  young  of  other  domestic  fowls,  however,  are  able  to 
walk  and  get  food  for  themselves  in  a  very  short  time.  The 
rapid  growth  of  their  feathers  is  soon  sufficient  as  a  protec- 
tive covering  to  keep  them  warm. 

Like  the  hair  or  fur  upon  animals  generally,  feathers  are 
an  outgrowth  of  the  skin.  They  serve  to  retain  heat  within 
the  body  of  the  bird.  The  body  temperature  in  birds  is 
much  higher  than  it  is  in  man  (110°  F.).  This  involves 
special  provisions  for  respiration  quite  unlike  those  in  the 
human  body.  The  amount  of  energy  developed  within  the 
bodies  of  birds  is  seen  strikingly  manifested  in  the  long- 
sustained  flights  of  homing  pigeons  which  are  estimated  to 
exceed  at  times  eighty  miles  per  hour. 

The  shedding  of  feathers  at  certain  seasons  is  called 
" molting.'7  The  growth  of  a  new  coat  of  feathers  is  rapid. 
There  is  more  or  less  of  a  change  of  coloring  as  the  plumage 
of  birds  is  renewed  with  "live"  feathers.  The  colorings  of 
the  male  and  female  birds  are  usually  different,  and  the 
characteristic  colorings  of  the  same  species  is  maintained  so 
fully  in  each  successive  generation  as  to  be  a  ready  means  of 
identification. 

The  variety  of  colors  in  plumage  is  largely  a  matter  of  the 
deposition  of  color  materials  (pigments)  in  different  portions 
of  the  plumage.  The  change  in  colors  as  viewed  from  differ- 
ent positions  is  a  phenomenon  that  in  Physics  is  called  light 
dispersion.  It  is  due  to  the  fact  that  the  barbs  and  barbules 
of  the  feathers  have  surfaces  marked  by  very  fine  lines  so 
close  together  as  to  break  up  the  light  that  falls  upon  them 
into  its  color  elements. 

The  feathers  of  the  tail  and  wings  of  a  bird  furnish  an 
excellent  illustration  of  "adaptation"  in  their  use  for  flight. 
Two  rows  of  interlocking  barbs  and  barbules  are  arranged 
along  opposite  sides  of  a  stiff  mid-rib,  the  whole  forming  the 


SURROUNDINGS  OF  THE  HOME  277 

vane  of  the  feather.      The  hollow  quill  is  both  light  and 
strong. 

The  legs  and  necks  of  wading  birds,  such  as  the  heron,  are 
greatly  lengthened;  the  feet  of  swimming  birds,  such  as 
ducks  and  geese,  have  the  toes  joined  by  a  web.  Birds  that 
perch  have  one  toe  of  the  four  opposite  to  the  other  three 
even  as  the  thumb  is  opposite  the  four  fingers  of  the  human 
hand.  With  some  birds  that  climb,  two  of  the  toes  are 
opposite  the  other  two. 

Birds  have  no  teeth.  The  food  when  swallowed  may 
lodge  and  remain  for  a  time  in  an  enlarged  portion  of  the 
food  passage  known  as  the  "crop",  where  it  becomes  more 
or  less  softened.  It  then  passes  on  into  what  corresponds 
to  the  stomach  ("the  gizzard")  where  by  action  of  the 
strong  muscular  walls  it  is  subjected  to  a  grinding  process. 
Sand,  gravel,  and  other  like  material  is  swallowed  by  fowls 
and  birds  to  aid  in  this. 

The  horn-like  bills  (beaks)  of  birds  are  of  varied  shapes 
and  degrees  of  strength,  and  are  adapted  to  the  kind  of  food 
upon  which  the  birds  live. 

In  the  humming  bird  the  bill  is  slender  and  much  elon- 
gated; in  ducks  and  geese  broad  and  much  flattened;  and  in 
hawks  and  eagles  it  is  powerful  enough  to  tear  the  flesh  of 
their  prey  when  once  their  claws  (talons)  have  grasped  it. 
The  bill  is  an  important  means  of  identification  of  species  of 
birds. 

Failure  in  food  supply  is  probably  one  of  the  reasons  why 
birds  migrate  on  the  approach  of  winter.  Their  return  to 
more  northerly  latitudes  in  the  spring  doubtless  involves 
other  causes.  In  preparation  for  these  migrations,  even  as 
in  nest  building,  birds  exhibit  an  instinct  that  occasions 
wonder.  Some  kinds  gather  in  flocks  numbering  thousands, 
taking  their  journey  only  after  days  of  seeming  preparation. 
With  some  kinds  of  birds  these  migrations  are  made  at  night, 


278  GENERAL  SCIENCE 

either  in  flocks  or  in  small  groups.  Few  of  them  will  be 
found  in  their  usual  haunts  following  one  of  these  migra- 
tions. These  journeys  in  many  cases  extend  over  distances 
of  hundreds  and  hundreds  of  miles,  and  often  are  over  vast 
stretches  of  water  as  well  as  of  land.  How  birds  can  be  so 
sure  of  their  course,  and  how  it  is  that  they  return  as  they 
oftentimes  do  season  after  season  to  the  same  places  of  abode, 
is  again  occasion  for  wonderment. 

The  skill  shown  by  each  successive  generation  of  birds  in 
nest  building  is  another  evidence  of  their  superior  intelligence. 
This  is  commonly  referred  to  though  not  explained  by  calling 
it  instinct.  The  manner  of  nesting  is  characteristic  of  the 
bird,  and  the  nest  serves  to  identify  its  builder.  A  pair  of 
young  birds  building  their  first  nest  construct  it  as  other 
birds  of  that  species  have  done  before  them.  This  remains 
true  even  where  young  birds  have  been  reared  wholly  apart 
from  their  kind.  Some  birds  build  nests  which  are  marvels 
of  ingenuity  and  skill  in  construction.  Their  selection  of  a 
place  for  the  nest  often  exhibits  the  greatest  cunning.  Many 
stories  are  told  of  the  deception  and  thievery  practised  by 
the  crow  when  captured  young  and  tamed  at  some  farm 
home.  Some  parrots  when  trained  show  a  marvelous  degree 
of  intelligence. 

Birds  feed  very  largely  upon  weed  seeds,  and  upon  insects. 
The  young  are  fed  insects  and  worms  quite  exclusively  for 
the  first  few  weeks.  Many  species  of  birds  live  almost 
wholly  upon  insects  when  obtainable,  using  fruits  and  seeds 
only  when  the  other  foods  fail.  The  value  of  birds  to  man 
may  be  calculated  not  in  the  number  of  insects  actually 
destroyed  for  food  during  the  whole  season  but  in  the  number 
which  would  otherwise  have  multiplied  from  those  destroyed. 
The  value  of  birds  to  man  in  holding  in  check  insect  pests 
and  weed  growths  is  greatly  underestimated.  The  horti- 
culturist is  unable  to  raise  marketable  fruit  without  con- 


SURROUNDINGS  OF  THE  HOME  279 

tinuous  warfare  upon  insect  enemies,  and  insect  plagues  cost 
the  country*  millions  of  dollars  a  year  in  a  decreased  yield 
of  the  farms.  These  losses  have  close  relationship  to  the 
wholesale  warfare  that  has  been  carried  on  for  years  against 
birds.  Much  of  this  killing  has  been  mere  wantonness  under 
the  name  of  ' '  sport. ' '  Very  largely  it  has  been  and  continues 
to  be  in  utter  disregard  of  public  interests,  and  it  is  a  waste 
of  public  wealth.  Birds  are  necessary  to  conserve  the  food 
supply  of  the  country. 

Aside  from  these  interests,  birds  rightly  claim  protection 
and  considerate  care  by  reason  of  their  beauty  of  form  and 
movement,  and  the  great  enjoyment  afforded  in  their  songs. 
Collections  of  birds'  eggs  by  school  children  should  not  be 
allowed.  National  legislation  against  traffic  in  the  plumage 
of  birds  for  millinery  should  be  strictly  enforced.  Some  of 
the  kinds  of  birds  of  most  beautiful  plumage,  both  in  this 
country  and  abroad,  have  been  largely  or  wholly  extermi- 
nated by  the  demands  of  fashion.  Cats  and  squirrels  are 
natural  enemies  of  birds.  The  English  sparrow  brought  to 
this  country  in  1850-51  is  a  good  illustration  of  the  survival 
of  those  forms  of  life  best  fitted  to  existing  conditions.  But 
it  is  a  poor  exchange  to  lose  our  American  songsters  and  to  get 
this  quarrelsome  nuisance  as  the  representative  of  bird  life 
in  our  daily  round  of  life  experiences. 

SUMMARY 

Studies  of  birds  can  very  successfully  be  carried  on  by  comparison 
after  having  made  a  detailed  study  of  some  one  or  more  kinds  as  types. 
A  study  of  some  one  of  the  domestic  fowls  may  be  included  in  this  list. 

Birds  may  be  characterized  as  feathered  bipeds  hatched  from  eggs 
laid  by  a  parent  bird. 

The  plumage  of  birds  is  wonderful  in  its  structure,  and  in  its  adapta- 
tion for  flight,  and  as  a  covering  to  protect  from  wet  and  cold.  In  many 
cases  the  plumage  is  striking  in  its  beauty  of  coloring  and  of  form. 


280  GENERAL  SCIENCE 

Some  kinds  of  birds  of  most  beautiful  plumage  have  become  nearly 
or  quite  extinct  because  of  their  use  for  millinery  purpose's. 

The  necks,  legs,  feet,  wings,  and  bills  in  different  kinds  of  birds  are  so 
modified  as  to  fit  them  for  their  special  manner  of  life.  It  is  an  illus- 
tration of  the  effect  of  environment  upon  animal  life,  and  of  adaptation 
to  needs. 

Birds  raised  entirely  apart  from  any  of  their  kind  exhibit  what  is 
called  instinct  in  their  skill  in  nest  building,  and  in  their  migratory 
habits.  They  do  just  as  if  they  had  been  taught  by  the  parent  birds. 
This  transmission  of  traits  from  generation  to  generation,  and  the  cer- 
tainty with  which  these  traits  will  be  reproduced  in  succeeding  genera- 
tions, is  one  of  the  marvels  of  all  plant  and  animal  life.  It  is  of  the 
utmost  importance,  too,  in  mankind. 

The  migration  of  birds  appears  due  very  largely  to  failure  in  the  food 
supply,  or  to  need  for  an  improvement  in  it. 

The  great  value  of  birds  as  a  check  upon  insect  pests  may  be  calcu- 
lated in  the  vast  numbers  of  insects  that  might  have  multiplied  from 
those  destroyed  early  in  the  season  when  fruits  and  seeds  are  scarce  as 
food  for  the  birds. 

Exercises 

1.  Upon  what  do  birds  largely  subsist?     Account  for  their  migrations. 

2.  In  what  respects  are  birds  (a)  useful  to  men;  (b)  harmful?     Name  reasons 
other  than  their  usefulness  for  protecting  birds  and  caring  for  them. 
What  exceptions  are  there  to  the  rule  "Protect  the  birds"? 

3.  The  extended  use  of  the  plumage  of  birds  for  millinery  has  resulted  in 
what  conditions?     What  only  has  caused  any  considerable  check  upon 
this  evil?     How  is  it  that  extreme  cruelty  is  so  often  incident  to  the 
collection  of  the  plumage  of  birds  for  millinery  purposes? 

4.  What  is  meant  by  a  "closed  season"  for  game  birds? 

6.  Name  various  natural  enemies  of  the  song  birds.     Tell  how  some  degree 

of  protection  against  these  may  be  afforded  the  birds. 
6.   How  do  birds  make  ample  returns  for  the  shelter  afforded  them  in  the 

trees  about  a  home? 


XH.  SOME   CONDITIONS   AFFECTING  INDUSTRIAL 

LIFE 

CHANGES  IN  MANNER  or  LIVING 

By  means  of  the  labor  of  men,  either  with  or  without  the 
extensive  use  of  machinery,  raw  material  from  the  mineral, 
vegetable,  and  animal  kingdoms  is  made  more  and  more 
serviceable  to  mankind.  At  the  same  time  it  becomes  more 


FIG.  89. — The  first  railway  service  in  the  United  States. 

costly.  Manufactures  as  products  of  man's  labor  add  to  the 
wealth  of  the  nation  that  manufactures  them.  More  of  the 
necessities  of  life  can  be  secured  in  exchange  for  them.  Pass- 
ing these  same  articles  on  from  seller  to  buyer,  without  any 
change  upon  them  other  than  transportation,  also  adds 
much  to  their  final  cost  to  the  consumer  though  the  goods 
remain  just  as  when  they  left  the  hands  of  the  producer. 
Transportation  facilities  by  highways,  railways,  and  water- 
ways directly  affect  the  welfare  and  prosperity  both  of  the 

281 


282  GENERAL  SCIENCE 

consumers  in  any  community  and  of  those  who  as  producers 
must  send  their  products  long  distances  to  market. 

People  are  often  classified  as  either  producers  or  con- 
sumers. The  agriculturist  by  expenditure  of  time,  labor, 
and  skill  may  appropriate  to  his  gain  the  raw  materials  from 
earth,  air,  water,  and  sunshine  for  his  crops  of  wheat,  corn, 
and  fruit.  He  may  transform  these  in  turn  into  meat  and 
dairy  products.  In  a  very  true  sense  he  is  to  this  extent  a 
producer.  The  men  who  dig  coal  and  iron  ores,  and  the  iron 
manufacturer  who  turns  these  raw  materials  into  forms  in- 
dispensable in  modern  life,  are  also  producers  of  natural 
wealth.  But  at  the  same  time  the  miners,  furnace  men, 
and  the  iron  manufacturer  himself  as  consumers  are  depend- 
ent upon  the  agriculturist  for  their  daily  food. 

Those  who  are  engaged  in  trade  and  transportation,  and 
those  to  whom  merchandise  is  finally  sold  for  use,  may  be 
classified  as  consumers.  They  may  in  some  cases  be  the 
very  same  people  who  produced  the  raw  material  itself  on 
the  farm  and  in  the  mines.  The  shoe  manufacturer  may  be 
considered  as  a  producer  of  wealth,  but  he  and  his  workmen 
are  classed  among  the  consumers  with  reference  to  food 
supplies.  No  studies  of  the  production,  transportation, 
and  consumption  of  raw  material  and  of  manufactured 
products,  in  connection  with  the  industries  and  occupations 
of  the  people  of  any  community  or  nation,  can  be  carried 
far  without  a  discussion  of  economic  problems  involving  the 
principles  of  Political  Economy. 

A  city  or  nation  occasionally  faces  a  condition  such  as  that 
involved  in  the  " strike"  of  a  large  body  of  those  engaged  in 
its  transportation  service.  The  railway  systems  of  the 
country  may  be  paralyzed  for  lack  of  men  to  operate  them. 
At  these  times  not  only  may  the  lives  of  citizens  be  jeopard- 
ized, their  comfort  and  welfare  disregarded,  but  the  stability 
of  government  and  the  enforcement  of  its  laws  may  be  im- 


CONDITIONS  AFFECTING  INDUSTRIAL  LIFE  283 

periled.  The  complexity  of  modern  life  makes  necessary 
a  widespread  intelligence  concerning  the  questions  of  hours 
of  labor,  of  wage  earning,  and  of  trade  conditions. 

This  state  of  affairs  is  in  sharp  contrast  to  the  simplicity 
and  independence  in  manner  of  life  during  the  earlier  years 
of  our  country's  history.  Then  it  was  a  common  thing  for 
a  family  to  keep  a  few  sheep  whose  wool  when  carded  was  spun 
at  home  and  woven  into  cloth  there.  This  cloth  was  then 
cut  up  in  the  home  and  made  into  wearing  apparel  for  the 
members  of  the  family.  Now  the  spinning  and  weaving  is 
done  in  great  factories,  and  all  woolen  clothing  is  usually, 
purchased  ready-made. 

In  those  early  times  when  a  farmer  butchered  a  beef  the 
meat  was  cured  at  home,  the  tallow  was  prepared  ("  ren- 
dered") at  home  and  made  into  candles  by  the  family,  and 
all  waste  fats  were  used  for  making  the  family  supply  of 
soap.  The  hide  of  the  animal  was  made  into  leather  at  a 
local  tannery,  and  footwear  for  the  family  was  made  from  it 
by  tHe  neighborhood  shoemaker.  The  corn  and  wheat  for 
family  use  as  food  was  ground  at  a  nearby  mill,  and  any 
balance  of  these  foodstuffs  was  fed  to  the  stock  on  the  home 
place.  To-day  the  farmer  buys  shoes  and  clothing  ready- 
made,  and  the  meat  and  flour  he  needs  are  bought  from 
dealers  in  town. 

Such  changes  as  these  in  the  general  manner  of  life  of  the 
people  of  the  United  States  were  especially  rapid  in  the  last 
half  of  the  nineteenth  century.  A  new  empire  of  agricultural 
industry  and  wealth  arose  in  the  valleys  of  the  Mississippi 
and  the  Missouri.  Chickens  in  New  England  and  cows  in 
New  York  State  were  fed  corn,  wheat,  and  mill  products 
grown  in  Missouri,  Kansas,  Iowa,  Nebraska,  and  the  Dakotas. 
The  cost  of  these  foodstuffs  after  transportation  was  less  than 
the  cost\>f  production  on  the  eastern  farm.  Cattle  fattened 
in  the  far  West  were  slaughtered  at  Kansas  City,  Omaha,  or 


284  GENERAL  SCIENCE 

Chicago,  and  the  meat  shipped  to  eastern  towns  for  sale  at 
prices  as  low  as  the  cost  of  production  there. 

Any  simple  statement  of  changes  in  the  life  of  the  nation 
due  to  these  causes,  and  to  an  annual  immigration,  often 
exceeding  a  million  a  year,  is  not  broad  enough.  Any  dis- 
cussion of  the  economic  conditions  involved  in  these  changes 
in  production,  trade,  and  industry,  and  any  discussion  of  the 
geographical  conditions  that  have  directed  and  modified 
these  new  currents  of  national  life,  is  incomplete  in  itself. 
Underlying  it  all,  and  interwoven  with  all  this  progress  to- 
ward more  of  the  comforts  and  conveniences  in  life  and  less 
of  its  hardships,  is  a  degree  of  scientific  achievement  that  is 
marvelous.  In  its  applied  form,  as  translated  into  terms  of 
machinery,  science  has  multiplied  the  working  capacity  of 
individuals  in  many  cases  a  thousand  fold,  and  has  shifted 
the  burden  of  large  parts  of  the  world's  labor  from  man  to 
machines.  Inventive  genius,  applying  the  results  of  scien- 
tific discoveries,  has  perfected  machines  that  demand  workers 
of  the  highest  intelligence  to  operate  and  care  for  them. 
Unskilled  labor  is  ever  put  more  and  more  at  a  disadvantage 
in  this  scientific  age. 

A  striking  illustration  of  development  of  natural  resources 
under  stimulus  of  applied  science  and  invention,  and  of  a 
revolution  wrought  in  the  social,  agricultural,  and  industrial 
life  of  the  United  States  in  connection  with  such  development, 
is  seen  in  the  widespread  use  of  automobiles,  motor  trucks, 
and  gasoline-driven  machinery  of  all  kinds.  Man's  mastery 
of  the  air  waited  upon  the  development  of  light  but  powerful 
engines  using  petroleum  oils  for  fuel.  It  was  necessary  that 
these  heavier-than-air  machines  be  given  a  velocity  not  only 
sufficient  to  sustain  themselves,  but  to  make  long  flights  possi- 
ble even  when  carrying  passengers  or  other  load.  Marvelous 
as  was  the  rapidity  in  introduction  and  use  of  gasoline 
machinery  for  factory,  farm,  and  highway,  the  development 


CONDITIONS  AFFECTING  INDUSTRIAL  LIFE  285 


FIG.  90. — Interior  of  a  silk  mill.     (By  Underwood  and  Underwood.) 


286 


GENERAL  SCIENCE 


of  aerial  navigation  under  stress  of  a  world  war,  and  its  as- 
sured usefulness  in  times  of  peace,  is  occasion  for  even  greater 
wonder. 

Petroleum  as  obtained  from  deeply  drilled  wells  is  a  heavy 
liquid  of  a  characteristic  disagreeable  odor,  and  often  times 
is  greenish  in  color.  The  rise  of  the  petroleum  industry  in 
the  United  States  dates  from  wells  driven  in  1859  near 

Million    Barrels 


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FIG.  91. — Production  of  petroleum  in  the  United  States  from  1860  to  1910. 

Titusville,  Pa.  The  accompanying  graph  shows  the  rapid 
increase  in  its  production  in  this  country.  For  years  kero- 
sene was  one  of  the  most  important  products  of  the  refining 
of  petroleum.  Its  use  in  lamps  for  household  illumination 
became  world-wide.  Knowledge  of  the  importance  of 
numerous  other  products  from  the  refining  of  petroleum, 
and  of  the  manner  of  their  separation  from  one  another,  may 
be  gained  in  the  study  of  Chemistry.  Among  these  products 


CONDITIONS  AFFECTING  INDUSTRIAL  LIFE 


287 


are  the  aniline  dyes,  and  long  lists  of  substances  handled  in 
the  drug  trade. 

The  oil  fields  of  Indiana  were  opened  in  1897,  of  Texas  in 
1901,  of  California  in  1903,  and  of  Oklahoma  in  1905.  The 
petroleum  from  the  Texas  and  California  fields  has  extensive 
use  as  fuel  supply  for  shipping  and  for  locomotives  in  rail- 
way service.  So  important  is  an  ample  supply  of  petroleum 


FIG.  92. — Location  of  the  larger  oil  fields  of  the  United  States. 

for  the  navies  of  the  world  and  for  shipping  generally  that  all 
large  sources  of  its  supply,  including  on  this  continent  the 
rich  oil  fields  of  Mexico,  are  subjects  of  greatest  concern  in 
international  relationships. 

From  the  development  of  the  petroleum  industry  in  the 
United  States  has  come  great  added  wealth  to  the  nation 
as  a  whole.  But  it  has  concentrated  vast  fortunes  in  the 
hands  of  a  few  individuals,  and  has  given  rise  to  business 
organizations  exercising  far-reaching  influences  in  trade  and 
commerce,  and  in  the  social  and  economic  conditions  affecting 
the  lives  of  people  generally.  As  in  the  case  of  coal  with 
which  it  is  so  closely  related  in  chemical  nature  and  geological 


288  GENERAL  SCIENCE 

history,  petroleum  is  a  natural  resource  limited  in  amount. 
Its  restricted  production  and  possible  exhaustion  may  reason- 
ably be  forecasted. 

The  use  of  farm  machinery  when  operated  by  horses  has 
more  than  doubled  the  area  of  farm  land  that  one  man  can 
cultivate.  Because  of  the  wide  use  of  farm  machinery  not 
as  many  men  are  needed  in  the  farming  districts.  Farms 
which  were  sufficiently  large  when  labor  was  done  by  hand 
have  proven  unprofitable  when  expensive  machinery  is 
employed.  Abandoned  farm  buildings  are  not  infrequently 
seen  in  many  sections  of  the  United  States,  bearing  witness 
to  a  readjustment  of  rural  conditions  inevitable,  perhaps, 
but  not  altogether  satisfactory.  In  many  sections  there  has 
been  a  marked  increase  in  the  size  of  farms,  and  a  decrease 
in  the  number  of  families  living  on  them. 

The  standards  of  living  during  this  time  underwent  change. 
People  demanded  more  of  the  comforts  of  life  in  their  homes, 
and  less  of  the  hardships  and  the  drudgery  endured  by  the 
forefathers  in  an  undeveloped  new  country.  Farms  that 
had  supported  successive  generations  of  prosperous  American 
country-folk  were  declared  to  be  no  longer  desirable  places 
of  residence.  Better  schools  were  provided  for  children 
in  the  towns.  There  was  the  possibility  in  towns  and  cities 
of  steady  employment  in  office,  store,  shop,  mill,  or  factory 
for  women  as  well  as  men.  An  income  from  wages  was  not 
subject  to  losses  by  bad  weather  and  crop  failures.  All  these 
conditions,  together  with  the  various  advantages  that  town 
life  offered  in  other  ways,  contributed  to  a  phenomenal  drift 
in  population  from  the  farms  to  the  cities,  especially  in  the 
eastern  portion  of  the  United  States1.  There  was  a  radical 

1  The  Census  Reports  of  the  United  States  by  decades  show  the  percentage 
of  the  population  of  the  country  resident  in  cities  and  towns  of  2500  or  more 
inhabitants  as  follows: 

1880  1890  1900  1910 

29 . 5  per  cent          36 .  i  per  cent         40 . 5  per  cent         46 . 3  per  cent 


CONDITIONS  AFFECTING  INDUSTRIAL  LIFE  289 

change  in  the  character  of  the  rural  population  and  of  rural 
life  generally  over  widespread  areas. 

SUMMARY   ' 

The  relationship  is  very  close  between  the  geography  of  any  region, 
the  occupations  of  its  people,  and  their  advancement  in  trade,  industry, 
and  civilization. 

As  the  population  of  a  country  becomes  more  dense,  complex  ques- 
tions arise  affecting  transportation,  cost  of  living,  and  employment  of 
labor.  There  must  be  adjustments  of  government  to  varied  interests 
that  are  more  or  less  conflicting.  Some  knowledge  of  the  college  sub- 
jects of  Economics  and  of  Sociology  becomes  highly  desirable.  But  one 
does  not  have  to  make  a  study  of  these  branches  in  order  to  understand 
a  great  deal  about  the  mutual  dependence  of  the  people  of  different 
sections  of  any  country,  and  of  the  people  of  all  parts  of  the  world. 

Within  the  half  century  following  the  Civil  War  a  marvelous  develop- 
ment occurred  in  the  United  States  affecting  its  industries,  population, 
wealth,  and  the  manner  of  life  of  its  people.  The  history  of  this  period 
will  strongly  emphasize  the  development  of  natural  resources  that  took 
place,  and  the  extensive  changes  and  readjustment  of  conditions  that 
occurred,  incident  to  the  introduction  and  use  of  machinery.  An 
understanding  of  these  changes  in  the  life  of  the  American  people  is 
impossible  without  a  knowledge  of  the  scientific  achievements  of  this 
period,  and  of  the  years  just  preceding  it. 

Exercises 

1.  Mention  some  of  the  differences  involved  in  making  a  living  by  business 
or  professional  life,  and  by  working  at  a  trade. 

2.  What  general  relationship  exists  between  transportation  facilities  and  the 
size  of  towns? 

3.  What  very  largely  affects  the  choice  of  location  and  the  development  of 
any  particular  manufacturing  industry? 

4.  What  are  the  serious  disadvantages  to  any  country  in  having  its  industries 
centralized  rather  than  widely  distributed? 

5.  Give    some  of  the  principal  reasons  why  people  move  into  towns  and 
cities  to  live.     What  are  some  of  the  decided  advantages  of  life  in  rural 
districts? 

6.  What  conditions  affecting  the  workers  in  mill,  factory,  or  shop  correspond 
to  the  uncertain  returns  from  farming? 

19 


2  go 


GENERAL  SCIENCE 


7.  If  an  annual  inventory  be  made  by  the  wage  earner  and  by  the  farmer, 
even  as  by  the  business  man,  what  in  each  case  would  constitute  a  showing 
of  profits? 

8.  Upon  what  besides  taxable  property  does  the  wealth  of  any  community 
depend? 

SOCIAL  AND  ECONOMIC  CONDITIONS  AFFECTING 
THE  WAGE  EARNER 

Incident  to  the  rapidity  with  which  changes  in  industrial 
life  have  been  brought  about  in  this  country  have  come  many 


FIG.  93. — Thriftlessness  and  poverty. 

evils.  Enlightened  citizenship  demands  that  provision  be 
made  for  sanitary  conditions  of  life  everywhere,  especially 
in  the  over-crowded  sections  of  great  cities.  Ordinary 
prudence  demands  such  thrift  that  when  periods  of  depres- 
sion come  to  the  business  and  industrial  world,  even  as  crop 
failures  come  to  the  farmer,  no  extreme  poverty  and  distress 
will  be  experienced.  Poverty  is  a  common  accompaniment 


CONDITIONS  AFFECTING  INDUSTRIAL  LIFE  291 

of  thriftlessness  and  inefficiency,  and  freedom  for  many 
hours  a  day  from  all  demands  of  labor  is  not  necessarily 
conducive  to  better  living. 

We  wonder  at  statements  made  by  competent  authorities 
that  four  millions  of  people  in  this  country  are  dependent 
upon  charity,  public  or  private,  and  that  ten  millions  more 
are  underfed  and  handicapped  in  life  because  of  the  condi- 
tions under  which  they  live.  Much  can  be  done  to  remedy 
these  conditions  by  means  of  public  enlightenment  and 
far-reaching  economic  legislation.  The  individual  himself, 
however,  is  always  responsible  for  making  the  most  of  all 
opportunities  for  self -betterment,  and  for  avoiding  whatever 
wastes  his  time,  means,  and  health1. 


xThe  following  are  the  "Financial  Life  Records"  of  one  hundred  average 
men  who  at  twenty-five  are  healthy,  vigorous,  of  good  mental  and  physical 
capacity,  and  without  means  of  support  other  than  their  own  ability  and 
efforts,  as  shown  in  data  compiled  and  published  by  the  Savings  Bank  Sec- 
tion of  the  American  Bankers  Association: 

At  the  age  of  25      35      45       55       65       75 


Dead  

5" 

16 

20 

g 

6* 

Wealthy  

10 

•2 

i 

C 

•2 

In  good  circumstances 

IO 

•2 

In  moderate  circumstances  
Those  without  financial  means  ...     100 
Not  self-supporting  

40 

35 

65 

16 

46 
30 

6 
53 

34 

IOO   IOO   IOO   IOO   IOO   IOO 

Of  the  sixty-three  dead  at  seventy-five  years  of  age,  sixty  left  no  estate 
(property  of  value  sufficient  for  matter  of  record).  Those  listed  as  not  self- 
supporting  were  more  or  less  dependent  upon  children,  relatives,  or  charity. 

Records  of  Surrogate's  Courts  show  that  for  every  100  men  who  die  the 
estates  of  three  are  $10,000  or  above;  of  fifteen  are  from  $2,000  to  $10,000;  of 
eighty-two  are  of  no  considerable  value.  Of  every  100  widows  eighteen  are 
left  in  comfortable  circumstances;  forty-seven  are  obliged  to  go  out  to  work 
for  a  living;  and  thirty-five  are  left  dependent,  or  in  want. 

In  1914  in  the  United  States  there  was  spent  for  tobacco  520  millions  of 
dollars,  and  for  alcoholic  beverages  1720  millions  of  dollars. 


292  GENERAL  SCIENCE 

The  hours  of  freedom  from  labor,  both  of  men  and  of 
women,  should  yield  rest  and  refreshment  and  intellectual 
advancement,  and  not  be  spent  in  ways  that  dissipate 
money,  time,  energy,  or  ability.  The  thrifty  farmer  a  half 
century  ago  was  astir  at  five  o'clock  in  the  morning,  and  abed 
at  eight  o'clock  at  night.  Few  if  any  of  these  intervening 


FIG.  94. — Benjamin  Franklin 

hours  had  been  used  for  anything  other  than  labor  for  the 
family  welfare.  The  hours  of  a  day's  labor  for  the  housewife 
were  even  longer.  The  vigor  and  vitality,  the  worth  and 
excellence  of  these  people,  made  possible  the  conditions  of 
life  that  we  enjoy.  Right  use  of  the  time  and  energy  secured 
by  a  release  from  the  drudgery  of  life  means  a  higher  civiliza- 
tion, and  larger  individual  happiness;  its  wrong  use  may  mean 
degradation  for  the  individual,  and  destruction  to  society. 
One  great  purpose  of  attendance  upon  schools  is  to  learn 


CONDITIONS  AFFECTING  INDUSTRIAL  LIFE  293 

what  are  wise  courses  to  follow  in  life,  and  how  most  advanta- 
geously to  use  the  accumulated  knowledge  of  mankind. 

The  lessons  of  chief  importance  in  school  and  home  alike 
are  those  that  teach  the  wisdom  of  the  ages  concerning 
human  conduct — that  knowledge  which  the  later  experiences 
of  life  only  verify  and  emphasize.  Any  education  is  faulty 
and  incomplete  which  does  not  include  instruction  and 
practice  in  those  ways  of  life  often  referred  to  as  its  " virtues"1. 
These  cannot  be  fully  taught  or  sufficiently  practised  in 
school  alone.  Maxims  such  as  are  named  below  characterize 
a  well-ordered  life.  They  are  applicable  to  all  individuals 
in  all  the  walks  of  life: 

Avoid  those  indulgences  that  lead  one  to  live  beyond  his  means.  Choose 
those  pleasures  in  life  which  are  healthful,  and  which  cost  little  in  money 
and  effort. 

Abhor  waste  of  any  kind — waste  of  strength,  or  time,  or  means.  Remember 
that  one's  savings  rather  than  his  income  measures  his  increase  in  wealth, 
and  that  more  wisdom  is  necessary  to  spend  wisely  than  to  save. 

Choose  that  kind  of  an  education  which  shall  aid  in  living  a  more  efficient 
and  wisely  ordered  life.  The  worth  of  an  education  to  anyone  is  largely  meas- 
ured by  what  kind  of  a  person  it  helps  him  to  become,  and  by  what  he  is  en- 
abled to  accomplish  because  of  it. 

Make  no  exchange  of  health  for  pleasure,  wealth,  or  position.  He  who 
makes  so  bad  a  bargain  finds  his  attainment  worthless  for  lack  of  health. 

Avoid  any  conduct,  any  business  practice,  any  traffic  legal  or  illegal,  that 
advances  the  interests  of  one  person  or  class  at  the  expense  of  another,  and 
results  in  harm  to  others  rather  than  their  good2. 

" Sayings"  such  as  these  sum  up  invaluable  experiences 
of  mankind.  They  correspond  to  the  truths  or  " facts" 

1  Every  generation  of  American  boys  and  girls  should  become  familiar 
with  the  form  and  significance  of  some  of  the  sayings  of  Benjamin  Franklin 
statesman,  publicist    and  scientist.     Some  of  his  "wisdom"  as  it  affected 
American  home  life  of  earlier  generations  may  be  found  in  "Poor  Richard's 
Almanac".     (Houghton,  Mifnin  Company:  Boston.     Paper,  fifteen  cents.) 

2  Such  courses  may  be  classed  as  criminal  in  character  whether  as  a  business, 
trade,  or  practice.     However,  there  is  need  to  distinguish  carefully  between 
practices  fundamentally  criminal,  though  often  legalized,  and  the  person 
engaged  in  them  who  may  be  innocent  of  any  criminal  intent. 


294  GENERAL  SCIENCE 

upon  which  the  scientist  must  base  his  theories,  and  the 
various  other  facts  which  business  and  professional  men  take 
into  consideration  in  formulating  their  procedure  in  the 
affairs  of  life.  It  is  as  necessary  to  take  them  into  account 
in  one's  manner  of  living  as  it  is  for  the  scientist  to  take 
account  of  the  facts  that  affect  his  theories  and  his  practice. 
To  ignore  the  realities  of  human  existence,  and  to  fail 
to  adjust  conduct  to  them,  is  as  if  the  scientist  failed  to  make 
his  theories  fit  the  facts  to  which  they  relate. 

There  should  be  direct  relationship  between  the  training 
of  the  laboratory  in  high  school  science,  and  a  preparation 
for  those  activities  in  which  one  may  engage  later  in  life. 
This  relationship  can  be  wholly  apart  from  any  skill  acquired 
in  handling  apparatus  and  machines.  In  the  affairs  of  life, 
as  in  the  laboratory  and  study  room  at  school,  the  particular 
difficulty  or  "problem"  that  demands  attention  at  any  time 
requires  ability  to  get  the  facts  bearing  upon  it,  and  ability 
to  discriminate  in  the  relative  importance  of  these  facts. 
It  is  necessary  to  decide,  too,  the  course  to  be  pursued  in 
view  of  one's  understanding  of  the  facts  so  that  labor  of 
hand  and  head  shall  count  most.  When  any  such  plan  of 
action  fails  to  give  the  results  desired,  then  there  must  be 
ability  and  willingness  to  review  the  whole  situation,  to 
correct  errors  in  fact  and  in  judgment,  and  to  undertake 
anew  the  application  of  the  changed  plan.  This  in  a  simple 
way  is  the  procedure  of  the  scientist  in  making  advances  in 
learning.  It  is  the  course  pursued  by  successful  business 
and  professional  men,  and  it  is  a  course  which  begun  in 
school  may  be  continued  throughout  life.  It  is  to  be  remem- 
bered that  one's  school  days  are  but  a  beginning  in  becoming 
educated. 

No  acquaintanceship  with  books  and  their  stores  of  human 
learning  is  a  substitute  for  industry.  Health  and  efficiency  at- 
tend upon  the  combined  exercise  of  body  and  brain.  Habits 


CONDITIONS  AFFECTING  INDUSTRIAL  LIFE  295 

of  industry  like  other  habits,  and  correct  notions  of  the  dig- 
nity of  labor,  are  largely  formed  in  childhood  and  youth. 
Idleness  too  commonly  leads  to  vice,  and  the  energies  of 
youth  demand  a  healthful  outlet  in  employments  suited  to 
age  and  strength.  To  expect  a  boy  or  girl  to  grow  up  in 
idleness  and  without  responsibilities  till  sixteen  years  of 
age  or  thereabouts,  and  then  at  once  to  become  a  steady 
efficient  worker,  is  to  ignore  human  experience  and  the  power 
of  habit. 


SUMMARY 

No  nation  can  be  considered  truly  prosperous,  and  no  social  condi- 
tions are  satisfactory,  where  everyone  regardless  of  occupation  may  not 
have  wholesome  surroundings  of  life  if  they  will,  together  with  ample 
provisions  to  safeguard  health  and  life. 

Perhaps  at  no  time  in  the  world's  history  have  its  workers  who  are 
industrious  and  thrifty  been  able  to  possess  so  much  that  contributes  to 
comfort  and  well-being  as  now.  To  this  condition  scientific  achieve- 
ment has  contributed  largely,  putting  within  reach  of  those  of  moderate 
means  what  in  former  times  was  available  to  few  if  to  any.  Many  of 
the  comforts  and  conveniences  and  furnishings  of  an  unpretentious 
modern  home  were  unknown  less  than  a  century  ago. 

The  large  use  of  machinery  for  doing  the  work  of  the  world  has  con- 
tributed to  lessening  the  hours  of  labor,  and  doing  away  with  much  of 
life's  drudgery.  Whether  work  is  a  curse  or  a  blessing  to  individuals, 
and  to  people  generally,  depends  upon  whether  or  not  it  uplifts  them  in 
physical,  intellectual,  and  moral  well-being.  Freedom  from  labor,  and 
many  hours  of  leisure  because  of  shortened  hours  of  labor,  must  be 
judged  in  the  same  way.  The  same  rule,  too,  can  be  applied  rigorously 
to  those  who  because  of  the  possession  of  wealth  find  it  unnecessary  to 
labor  for  a  livlihood. 

Advances  in  civilization,  and  improvement  in  the  life  of  any  indi- 
vidual, depend  in  large  measure  upon  avoiding  the  mistakes  of  those 
who  have  learned  by  experience.  It  is  foolish  not  to  be  guided  by  what 
others  have  learned.  One  of  the  chief  purposes  of  schools  is  to  bring  this 
knowledge  before  the  pupils  of  each  generation  for  their  benefit  and 
use. 


296  GENERAL  SCIENCE 

There  are  ways  of  acquiring  and  applying  knowledge  that  are  pecu- 
liarly scientific,  and  not  least  of  the  worth  of  a  training  in  science  studies 
is  a  "scientific  attitude"  of  mind  toward  all  the  affairs  in  life.  One  of 
its  characteristics  is  in  basing  opinions  upon  facts  only,  and  in  testing 
out  these  opinions  to  see  that  they  are  in  accord  with  facts.  This 
requires  ability  to  collect  and  associate  all  available  information  gained 
from  personal  experiences,  from  experimental  work,  and  from  books. 
Conclusions  thus  reached  may  be  followed  in  any  of  the  affairs  of  life 
with  reasonable  assurance  of  success. 


XIII.  THE  FARM 

POULTRY  AND  EGGS 

One  of  the  noticeable  differences  between  meat  from  the 
hen,  and  that  from  wild  fowls  generally,  is  its  color.  The 
domesticated  fowl  has  a  large  amount  of  white  meat  as  result 
of  less  use  of  the  muscles,  and  a  consequent  lessened  supply 
of  blood  to  them.  This  is  especially  true  of  the  muscles  of 
the  breast  which  are  used  in  flying.  The  great  weight  of 
the  domesticated  hen  makes  flight  for  any  considerable 
distances  impossible.  The  same  thing  is  largely  true  of 
domestic  turkeys,  geese,  and  ducks.  The  bone  structure  of 
the  domesticated  fowls  is  denser  and  stronger  in  order  to 
support  the  heavier  weight  of  body.  The  mounted  skeletons 
of  birds  of  flight,  such  as  the  various  songbirds,  show  when 
examined  a  remarkably  light  structure,  the  bones  commonly 
being  hollow.  The  quill  feathers,  too,  strong  but  light, 
show  a  wonderful  adaptation  for  use  in  flying. 

The  hen  walks  on  her  toes  which  terminate  in  nails  (claws) 
very  serviceable  in  scratching  for  food.  The  scaly  and  more 
or  less  featherless  part  of  the  leg  corresponds  to  the  human 
foot.  Through  it  pass  tendons  that  move  the  toes.  The 
muscles  of  the _" drumstick"  from  which  these  tendons  arise 
exhibit  in  their  color  and  development  the  great  use  the  hen 
makes  of  her  feet.  The  drumsticks  correspond  to  that 
part  of  the  human  leg  from  knee  to  ankle,  while  the  thigh 
bones  of  a  fowl  are  closely  joined  to  its  body  and  are  covered 
by  the  body  skin. 

297 


298  GENERAL  SCIENCE 

The  wings  correspond  to  the  arms  of  people,  and  both 
upper  and  lower  arm  bones  are  coveredfby  the  skin  of  the 
body.  Imagine  a  person  with  the  whole  length  of  arm  to 
the  wrist  doubled  upon  itself  and  tied  close  down  against 
the  body,  and  the  fingers  and  hand  covered  with  feathers. 
Then  consider  the  difficulties  experienced  in  efforts  to  feed 
one's  self  and  to  keep  clean.  The  neck  structure  in  fowls 
gives  a  wonderful  variety  in  movements  and  in  serviceable- 
ness,  securing  both  strength  and  flexibility.  One  use  of  the 
bill  (beak)  by  birds  and  fowls  is  in  keeping  their  feathers 
clean  and  in  place. 

The  leg  structure  of  birds  that  perch  (roost)  is  such  that 
the  weight  of  the  body  causes  the  toes  and  claws  so  to  grasp 
the  support  that  when  asleep  they  cannot  fall  off.  Dif- 
ferences in  the  kinds  of  domestic  fowls  due  to  breeding  is  a 
matter  of  importance  to  poultrymen. 

When  combined  with  the  care  of  the  home  garden,  the 
responsibility  associated  with  the  keeping  of  poultry  provides 
for  both  boys  and  girls  an  educational  training  at  home  as 
valuable  as  any  " course"  in  schools.  There  is  an  abundance 
of  literature  of  great  worth  upon  both  Gardening  and  Poultry 
Raising,  much  of  which  may  be  had  at  slight  outlay.  But 
the  educational  .value  of  these  occupations  for  boys  and  girls 
lies  in  the  initiative,  the  persistence,  and  the  good  judgment 
demanded  by  the  home  work.  It  combines  physical  and 
mental  effort  in  a  manner  similar  to  that  which  characterizes 
advancement  in  first-hand  study  of  the  sciences,  and  success 
in  the  affairs  of  life  generally. 

Agriculture  as  a  school  subject  needs  application  of  its 
teachings  even  as  does  Home  Economics.  It  may  be  secured 
in  part  at  least  through  the  care  at  home  of  a  flock  of  fowls, 
and  of  the  vegetables  in  the  garden.  This  is  in  addition  to 
caring  for  the  lawn,  the  fruit  and  flowers,  the  trees  and  shrub- 
bery about  the  home.  Along  with  the  increase  in  skill  and 


THE  FARM  299 

ability  in  this  work  there  should  be  developed  business 
habits  and  enterprise  quite  as  valuable  as  that  gained  in 
other  life  experiences. 

Both  poultry  raising  and  gardening  have  become  highly 
developed  industries  in  many  localities.  This  is  especially 
true  in  the  vicinity  of  cities  that  afford  good  markets.  In 
both  fields  of  effort  capital,  executive  ability,  and  a  clear 
understanding  of  the  conditions  and  details  of  the  business, 
are  necessary  to  success.  The  value  of  the  egg  production 


FIG.  95. — Feeding  the  flock. 

in  the  United  States  amounts  to  millions  of  dollars  annually. 
This  seemingly  negligible  source  of  national  wealth  is  an  item 
of  importance  in  the  cost  of  living  and  in  the  wholesomeness 
of  diet. 

A  chicken  when  hatched  has  bone  and  muscle,  beak  and 
claws,  skin  and  feathers,  eyes  and  internal  organs.  All 
these  have  been  developed  from  the  material  stored  within 
the  shell  as  food  for  the  life  germ  or  embryo.  The  more 
one  considers  it  the  more  wonderful  this  seems.  The  white 
of  the  egg  is  largely  albumen  and  water,  and  the  yolk  con- 
tains much  albumen.  This  albumen  is  one  of  the  important 
substances  in  the  class  of  foods  known  as  proteins.  It  hardens 


3oo 


GENERAL  SCIENCE 


when  heated  as  in  the  familiar  case  of  eggs  hard  boiled. 
In  the  process  of  digestion  when  acted  upon  by  the  gastric 


FIG.  96. — Candling  eggs. 


and  pancreatic  fluids  it  is  changed  to  peptone  which  more 
readily  dissolves  and  osmoses.  Chemically  albumen  is 
very  closely  related  to  a  substance  gluten  found  "~ 


in 


THE  FARM  301 

grains  and  to  casein  found  in  milk.  (See  pages  222, 
and  328.) 

When  a  food  solid  is  treated  with  strong  nitric  acid,  any 
protein  is  colored  yellow.  If  it  is  then  washed  free  of  the 
acid  and  dipped  into  strong  ammonia  water,  the  color  may 
change  to  orange.  A  piece  of  white  silk  ribbon  shows  these 
same  tests  for  protein,  while  a  white  cotton  fabric  is  un- 
affected. The  cotton  is  cellulose,  a  vegetable  fibre,  and  con- 
tains no  protein. 

The  preservation  of  eggs  from  times  of  over  abundance  and 
low  prices  to  other  times  when  the  supply  is  much  less,  has 
been  solved  for  the  large  centres  of  population  by  keeping 
great  quantities  of  eggs  in  cold-storage  warehouses.  From 
these  storehouses  they  can  be  supplied  for  sale  as  the  market 
requires.  Their  food  value  is  unchanged  if  they  have  been 
properly  cared  for,  though  they  may  be  somewhat  less  palat- 
able than  when  fresh.  Eggs  for  storage  should  be  chosen 
with  care,  and  any  not  strictly  fresh  must  be  rejected.  There 
is  much  more  food  in  a  dozen  large  eggs  than  in  the  same 
number  of  small  ones,  and  size  may  very  properly  be  con- 
sidered in  the  sale  price  of  eggs. 

The  quality  of  an  egg  as  to  age  and  fitness  for  food  can 
easily  be  determined  by  holding  the  egg  between  the  eye  and 
a  strong  light,  preferably  an  electric  light  shining  out  through 
a  hole  in  a  box  within  which  the  light  is  placed.  This  testing 
should  be  carried  on  in  a  darkened  room,  too,  so  that  one's 
sight  is  unaffected  by  any  light  other  than  what  comes 
through  the  egg.  With  a  little  practice  eggs  may  be  graded 
almost  as  fast  as  they  can  be  handled  since  with  a  little 
experience  the  condition  of  the  egg  is  known  at  a  glance. 

For  family  use  on  the  farm  the  home  product  is  often 
stored  in  large  jars  filled  with  a  solution  of  " water  glass", 
or  sodium  silicate,  by  means  of  which  the  pores  of  the  shell 
are  closed  to  air  and  to  the  germs  that  cause  decay.  In 


302  GENERAL  SCIENCE 

this  case  as  in  cold  storage  the  eggs  should  be  turned  from 
time  to  time  that  the  yolk  may  not  settle  to  one  side  and 
become  attached  to  the  shell.  Brooding  hens  turn  the  eggs 
upon  which  they  are  sitting,  and  when  eggs  are  hatched  in 
an  incubator  they  must  be  turned  one  or  more  times. 

SUMMARY 

The  hen  as  type  of  all  domestic  fowls  illustrates  the  modifications 
accomplished  in  animal  structures  by  long-continued  selective  breeding. 
Certain  characteristics  in  build,  coloring,  and  egg  production  have  been 
intensified  by  retaining  in  the  flocks  year  after  year  only  those  fowls 
which  exhibit  the  desired  characteristics  in  most  marked  degree. 

If  domesticated  fowls  were  turned  loose  and  allowed  to  run  wild  in  an 
uninhabited  region,  few  if  any  of  them  would  be  likely  to  survive  the 
conditions  for  which  they  long  before  had  become  unfitted.  It  is 
likely,  however,  that  if  any  should  survive  their  successive  generations 
would  rapidly  revert  to  the  smaller  more  active  forms  seen  in  the  differ- 
ent kinds  of  game  birds. 

A  study  of  the  skeleton  of  a  hen  in  comparison  with  the  skeleton  of 
a  human  being  shows  that  the  hen  walks  on  her  toes.  The  lower,  scaly, 
and  often  featherless  part  of  the  leg  corresponds  to  the  human  foot. 

Where  fowls  are  kept  too  closely  penned  up,  and  without  sufficient 
freedom  of  range,  they  are  less  hardy,  more  likely  to  sicken  and  die,  and 
are  often  infested  with  vermin.  Shelter  from  cold  and  wet  is  essential 
to  their  healthy  state. 

Most  of  the  contents  within  an  egg  is  material  for  the  nourishment 
and  growth  of  the  embryo.  The  chick  in  due  time,  when  the  necessary 
conditions  for  hatching  have  been  favorable,  acquires  the  strength  to 
break  the  shell  enclosing  it  and  to  make  its  way  out. 

The  growth  of  the  young  chick  from  the  embryo  stage  is  by  cell 
division  just  as  growth  occurs  in  the  human  body  and  in  plants.  A 
wonderful  thing  about  it,  however,  is  the  variety  of  the  organs  (masses 
of  cells  doing  the  same  kind  of  work  in  the  body)  that  are  made  out  of 
the  material  stored  in  an  egg. 

Eggs  may  have  in  them  all  this  stored  material  and  yet  be  worthless 
for  the  hatching  of  chickens  because  destitute  of  the  embryo.  Its 
development  when  the  egg  is  forming  involves  fertilization,  which  cor- 
responds to  the  fertilization  of  the  ovules  of  flowers  (page  265).  Seeds 


THE  FARM  303 

that  lack  the  embryo,  regardless  of  the  supply  of  food  stored  in  them  to 
nourish  the  growth  of  a  young  plant,  never  can  germinate. 

The  storage  of  eggs  for  considerable  periods  of  time  in  condition  fit 
for  food  takes  into  account  the  fact  that  their  shells  are  more  or  less 
porous,  and  are  an  insufficient  protection  from  the  germs  which  cause 
decay.  By  sealing  the  pores  in  the  shells  with  water  glass,  or  by  storing 
eggs  at  a  temperature  too  low  for  the  germs  to  multiply,  the  fitness  of 
eggs  for  food  may  be  maintained  for  long  periods  of  time.  They  may 
be  kept  from  times  when  eggs  are  abundant  and  low  in  price  till  when 
more  scarce  and  of  higher  market  value. 

Much  of  the  value  in  the  sales  of  eggs  and  poultry  in  the  United 
States,  amounting  as  these  sales  do  to  millions  of  dollars  annually, 
represents  thrift.  Non-productive  labor,  and  food  materials  for  fowls 
which  otherwise  might  be  wasted,  are  thus  turned  into  profit  for  the 
individual  and  wealth  for  the  nation. 

Where  poultry  raising  is  carried  on  as  a  business,  rather  than  an 
occupation  incidental  to  general  farming  or  as  a  pleasing  home  employ- 
ment, careful  attention  to  all  details  of  it  is  necessary,  and  considerable 
business  ability  is  required  in  order  to  make  it  a  success. 

In  agricultural  colleges  courses  in  poultry  raising  are  given  for  college 
credit.  Much  helpful  literature  is  available  free  or  at  little  cost, 
however,  so  that  ordinary  intelligence,  coupled  with  painstaking  care 
and  an  exercise  of  good  judgment,  will  win  success  in  the  school  of 
experience. 

Exercises 

1.  Is  there  any  relation  between  the  food  value  of  eggs  and  the  color  of  their 

shells? 

2.  What  are  the  best  ways  of  preserving  eggs  on  a  commercial  scale?   State 
what  strength  of  solution  of  "water  glass"  is  used  to  preserve  eggs. 
Which  are  the  best  months  for  the  storage  of  eggs?     What  purposes  are 
accomplished  in  the  storage  of  eggs? 

3.  Reproduce  a  diagram  showing  the  cross-section  of  an  egg,  and  on  the 
diagram  locate  (a)  the  shell;  (6)  the  outer  and  inner  membranes;  (c)  the 
thicker  and  thinner  parts  of  the  white;  (d)  the  chalaza;  (e)  the  lighter 
and  darker  parts  of  the  yolk;  (/)  the  germ  (embryo). 

4.  What  food  constituents  of  large  value  in  eggs?     For  what  foodstuff  are 
eggs  a  substitute?    What  foods  are  best  served  with  eggs  at  table?    What 
are  the  digestive  solvents  for  the  albumen  of  eggs?     What  per  cent  of 
water  is  there  in  eggs? 


304  GENERAL  SCIENCE 

5.  Name  several  cooked  foods  that  have  eggs  in  their  make-up.     Of  what 
use  are  eggs  in  making  coffee?     Why  is  it  that  the  fresh  shells  may  serve 
a  like  purpose? 

6.  What  eggs  other  than  those  of  hens  are  used  for  food?     To  what  uses  are 
spoiled  eggs  put?     How  is  this  possible? 

7.  Describe  how  eggs  are  "candled".     What  is  the  purpose  of  the  air  space 
found  in  the  large  end  of  the  egg?     What  is  the  relative  size  of  this  air 
space  in  fresh  and  in  stale  eggs? 

8.  To  what  countries  are  eggs  exported  from  the  United  States?     Account 
for  their  export  to  Canada  which  is  an  agricultural  rather  than  a  manu- 
facturing or  commercial  country. 

9.  Name  the  various  tissues  of  the  body  of  the  chick  when  hatched.     Out  of 
what  substance  within  the  egg  have  these  been  developed?     Ascertain 
the  literal  meaning  of  the  word  protein. 

10.  In  some  general  and  striking  way  express  the  annual  value  of  both  the 
poultry  and  egg  production  of  the  United  States  (or  of  your  own  State). 

11.  How  does  the  extent  of  the  poultry  industry  exhibit  national  as  well  as 
individual  prosperity? 

12.  Why  is  raising  ducks  and  geese  so  much  less  common  than  raising  hens? 
Why  are  so  few  turkeys  raised? 

13.  What  advanced  high  school  science  includes  a  study  of  the  structure  of 
domestic  fowls?     Why  should  studies  of  poultry  be  included  in  a  high 
school  course  in  agriculture? 

14.  What  is  true  of  the  physical  endurance  necessary  in  raising  poultry  as 
compared  with  the  demands  of  general  farm  work? 

15.  Name  several  of  the  breeds  of  fowls  commonly  kept  for  profit  by  poultry 
raisers.     Mention  some  of  the  well-defined  characteristics  of  each  kind. 

THE  HORSE 

Any  discussion  of  the  farm  would  be  incomplete  without 
a  study  of  the  horse.  As  one  of  man's  most  faithful  and 
serviceable  domesticated  animals,  the  horse  has  long  con- 
tributed in  large  measure  toward  the  production  and  distri- 
bution of  the  world's  food  supplies.  It  is  but  a  few  years 
since  the  horse  was  relieved  from  the  tasks  of  transportation 
on  street-car  lines,  and  as  the  sole  source  of  power  in  moving 
boats  over  inland  waterways.  The  stage  coach  was  long 
ago  replaced  by  the  railway,  and  now  even  in  warfare  the 
motor  truck  lessens  the  need  for  horses.  The  part  played 
by  the  horse  in  the  world's  history,  as  used  by  man  in  the 


THE  FARM  305 

ways  of  peace  and  for  purposes  of  conquest,  would  make  a 
most  interesting  narrative. 

The  horse  belongs  to  the  vertebrates,  or  animals  with 
spinal  columns,  and  is  in  the  division  known  as  mammals. 
To  this  group  belong  such  domestic  animals  as  cattle,  sheep, 
pigs,  dogs,  and  cats,  together  with  various  wild  beasts  such 
as  bears,  wolves,  lions,  tigers,  and  elephants.  The  whale, 
too,  is  a  mammal  and  suckles  its  young,  and  man  himself 
belongs  to  the  mammals.  On  the  other  hand,  fish  and  birds 
hatch  from  eggs. 

From  studies  of  the  remains  of  animals  found  buried  in 
the  earth's  strata  geologists  are  able  to  give  a  detailed  story 
of  the  ancestry  of  the  horse.  This  history  runs  back  through 
geological  periods  to  animals  entirely  different  in  appearance 
from  the  horse  of  historic  times.  This  evolution  of  the  horse 
as  it  is  called  is  an  illustration  of  the  changes  that  have 
occurred  in  plant  and  animal  forms  during  countless  ages. 
Those  forms  best  adapted  to  changing  conditions  have  sur- 
vived. They  have  perpetuated  the  characteristics  and 
organs  which  have  best  served  their  needs  and  have  been  in 
most  frequent  use.  Man  himself  has  develope'd  and  per- 
fected various  breeds  of  horses,  cattle,  poultry,  and  other 
animals,  and  a  no  less  wonderful  change  has  been  wrought  in 
the  kinds  and  qualities  of  plant  life  by  selective  breeding. 
The  achievements  of  the  last  half  century  in  improving  plants 
and  animals  for  man's  use  and  enjoyment  has  been  scarcely 
less  than  marvelous.  Horticulture,  animal  husbandry,  and 
general  agriculture  especially  have  profited  largely  by  well- 
directed  persistent  applications  of  scientific  knowledge  in 
these  respects. 

The  teeth  of  the  horse  in  front  are  powerful  incisors  in 
both  upper  and  lower  jaws,  enabling  it  to  bite  off  grass  rather 
than  pull  it  off  as  the  cow  must  do  because  of  lack  of  the 
upper  incisors.  The  back  teeth  of  both  horse  and  cow  have 


3o6 


GENERAL  SCIENCE 


grinding  surfaces  suited  for  the  use  of-  coarse  dry  fodder. 
Both  horse  and  cow  belong  to  the  "order"  of  animals  known 
as  the  herbivora,  as  contrasted  with  the  flesh-eating  carnivora 
such  as  the  dog,  cat,  and  tiger.  The  teeth  of  mammals 
vary  widely  in  number,  form,  and  arrangement.  The  canine 
teeth  of  the  carnivora  are  fitted  for  grasping  and  tearing  their 
prey.  Instead  of  being  set  closely  together  as  in  human 


FIG.  97. — Teeth  of  a  horse. 

beings  the  teeth  of  mammals  generally  are  more  or  less 
scattered  along  the  jaws.  In  the  horse  the  absence  of  teeth 
between  the  molars  in  the  back  of  the  jaw  and  the  incisors 
in  front  leaves  a  place  well  suited  for  the  bits  of  the  harness. 

SUMMARY 

Unlike  birds  and  the  domestic  fowls  which  hatch  from  eggs  laid  by 
the  parent  bird,  horses  belong  to  the  group  known  as  mammals  which 
bring  forth  their  young  alive,  and  nourish  them  on  milk  from  the  body 
of  the  parent. 

In  the  jaws  of  mammals  generally  the  teeth  are  more  or  less  scattered. 
Advantage  of  this  is  taken  when  the  horse  is  harnessed  for  driving. 
The  bits  are  put  into  its  mouth  in  a  place  where  teeth  are  lacking. 


THE  FARM  307 

The  teeth  of  flesh-eating  animals  are  characteristically  sharp  pointed, 
fitted  for  grasping  and  tearing  their  prey.  But  the  horse  belongs  to 
the  herbivora  with  broad  flat  molars  suited  for  grinding  coarse  vege- 
table fodder,  and  with  chisel-shaped  incisors  for  biting  off  grass  in 
feeding. 

The  horse  ranks  as  one  of  the  most  intelligent  of  the  lower  animals, 
and  is  capable  of  being  highly  trained.  As  one  of  man's  most  useful 
servants,  and  as  a  companion  obedient  to  all  demands  made  upon  him, 
the  horse  has  played  a  prominent  part  in  the  affairs  of  mankind. 

Exercises 

1.  What  has  early  training,  or  lack  of  it,  to  do  with  the  behavior  of  horses? 

2.  What  constitutes  "good  habits"  whether  in  persons  or  in  horses? 

3.  Name  several  uses  of  horses  for  which  automobiles  are  not  well  suited. 

4.  What  considerations  of  public  health  make  fewer  horses  in  town  and  city  a 
desirable  thing? 

COWS,    AND     THE     DAIRY     INDUSTRY 

The  cost  of  meat  as  a  regular  part  of  the  food  supply  of  an 
individual  and  a  family  is  a  matter  of  serious  consideration. 
The  industrial  development  of  the  country  and  the  conse- 
quent increase  in  its  population  of  consumers,  together  with 
the  conversion  of  lands  once  cheap  and  devoted  to  cattle 
raising  into  high-priced  farms  devoted  to  other  agricultural 
pursuits,  operates  even  in  times  of  peace  to  raise  meat  prices 
to  a  point  almost  prohibitive  to  those  of  small  incomes. 

So  complete  is  government  supervision  of  the  meat  prod- 
ucts of  the  great  packing  houses  that  there  is  little  need  of 
any  fear  of  the  wholesomeness  of  meat  sold  in  the  markets. 
It  is  in  the  prepared  forms  of  meat,  such  as  sausage,  that 
there  may  be  use  of  preservatives  and  of  adulterants  (cheaper 
material  as  a  "filler"). 

No  meat  should  ever  be  used  without  having  been  thor- 
oughly cooked.  From  insufficiently  cooked  lean  pork 
trichina  may  be  introduced  into  the  human  body  causing 
sickness  and  death.  Tapeworms  come  from  uncooked  fish, 


308 


GENERAL  SCIENCE 


beef,  and  pork.  The  high  temperature  of  the  cooking 
process  kills  these  larvae,  and  at  the  same  time  destroys 
any  other  living  germs. 

The  milk  supply  is  a  much  more  serious  problem  so  far  as 
purity  is  concerned.  It  is  one  of  the  chief  foodstuffs  of 
people,  especially  for  infants  and  small  children,  and  it  may 
easily  become  a  menace  to  health.  The  dairyman  is  indeed 
a  neighbor  to  us  all  in  his  care,  or  carelessness,  as  these  affect 


FIG.  98. — Pasteurizing  milk.     Heating  and  cooling  done  by  circulation  first  of 
hot  and  then  of  cold  water. 


our  health.  Since  it  is  almost  inevitable  that  town  dwellers 
are  dependent  upon  the  milkman  for  their  daily  supply, 
city  authorities  acting  as  Boards  of  Health  exercise  close 
supervision  over  the  conditions  under  which  milk  is  sold  in  a 
city.  The  use  of  stoppered  bottles  for  milk  should  always 
be  insisted  upon.  But  this  is  no  sufficient  guarantee  that 
the  bottles  may  not  have  been  carelessly  sterilized,  or  washed 
in  water  containing  disease  germs.  The  germs  of  typhoid, 


THE  FARM  309 

diphtheria,  scarlet  fever,  and  possibly  of  tuberculosis  may 
be  carried  by  milk  that  has  not  been  pasteurized,  i.e., 
heated  from  150°  to  160°  F.  and  kept  at  that  temperature  for 
twenty  minutes.  Milk  peddled  in  open  cans  and  buckets 


FIG.  99. — Dr.  Stephen  N.  Babcock,  inventor  of  the  test  for  determining 
the  per  cent,  of  butter  fat  in  milk.  (Courtesy  of  Agricultural  College,  Univer- 
sity of  Wisconsin.) 

is  always  to  be  avoided.     The  demand  for  a  pure  milk  supply 
of  necessity  increases  the  cost  of  milk  to  the  consumer. 

Modern  dairy  farming  with  its  high-priced  high-bred  cows, 
its  expensive  dairy  outfits  and  farm  buildings,  expensive 


310  GENERAL  SCIENCE 

farmlands,  and  high  wages  for  labor,  requires  large  capital 
and  much  business  ability  to  make  it  a  success.  There  must 
be  no  waste  in  by-products,  no  heavy  outlays  for  feed  that 
can  be  produced  on  the  home  farm,  no  waste  in  fertilizer  for 
keeping  this  farm  land  at  its  highest  productive  stage,  and 
no  failure  to  make  the  products  of  the  dairy  yield  the  best 
financial  returns.  In  other  words  successful  dairying  requires 
the  intelligence  and  business  ability  in  all  its  details  that 
any  successful  business  demands. 

Illustrative  of  the  industrial  changes  wrought  in  the  last 
generation  in  this  country  as  a  result  of  the  widespread  use 
of  machinery,  it  is  interesting  to  note  that  a  large  share  of 
the  butter  product  of  the  country  is  now  made  up  in  the 
cities  rather  than  on  the  farms  as  was  formerly  the  case. 
Suspended  in  the  watery  part  of  the  milk  are  finely  divided 
fat  particles.  They  are  held  in  this  condition  by  the  protein 
in  milk  known  as  casein.  Liquids  of  this  character  are 
called  emulsions.  By  the  use  of  cream  separators  at  the 
dairy  farm  the  butter  fat  is  taken  from  the  milk  and  sold  to 
representatives  of  some  creamery,  located  it  may  be  in  a 
distant  city,  where  the  butter  is  made  in  great  quantities 
by  machinery  instead  of  hand  labor.  The  milk  thus  left  on 
the  farm  is  fed  to  pigs  and  calves.  The  drudgery  of  butter- 
making  has  been  transferred  from  the  women  folks  on  the 
farm  to  an  admirably  equipped  factory  where  every  stage 
of  the  manufacture  into  butter  is  clean  and  sanitary. 

The  cow  in  lying  down  kneels  on  the  front  legs  first, 
with  the  hind  quarters  down  last,  reversing  the  order  in 
getting  up.  In  the  case  of  the  horse,  the  hind  quarters  go 
down  first  and  are  raised  last. 

Scarcely  any  of  the  non-edible  portions  of  the  carcasses 
of  cattle  are  wasted.  The  fat  is  not  only  used  in  cooking 
as  suet,  but  for  making  oleomargarine.  Portions  unfit  for 
these  uses  are  valuable  in  candle-making  and  in  the  manu- 


THE  FARM  311 

facture  of  soap.  The  hides  are  converted  into  leather. 
From  the  hoofs,  horns,  bones,  and  the  scrap  parts,  gelatine 
and  glue  are  made.  The  bones  are  ground  for  chicken  feed, 
and  for  fertilizer,  or  are  charred  to  be  used  as  boneblack  in 
refining  sugar  to  make  it  white.  Both  the  hair  and  the 
blood  have  their  uses. 


FIG.   100. — Pasteurizing  apparatus  for  use  in  a  home. 


SUMMARY 


Meats  of  all  kinds  must  be  thoroughly  cooked  to  destroy  any  trichinae 
there  may  be  in  .the  lean  meat  from  the  hog,  or  tapeworms  in  the  lean 
meat  from  cattle.  Cooking  is  likely  to  render  harmless  any  poisonous 
products  present. 

So  readily  does  milk  serve  as  a  carrier  of  germs  of  such  diseases  as 
typhoid  and  diphtheria  that  utmost  precautions  must  be  observed 
concerning  the  care  of  it  from  milking  time  to  its  delivery  to  the  con- 
sumer. No  one  having  an  infectious  disease  should  be  permitted  to 
have  anything  to  do  with  handling  milk.  All  dairy  utensils  must  be 
thoroughly  sterilized  before  use,  and  only  water  known  to  be  uncon- 
taminated  should  ever  be  used  in  washing  and  rinsing  them. 

Milk  from  which  the  butter-fat  has  been  separated  for  sale  to  butter- 
making  establishments  is  kept  on  the  farm  for  use  as  food  for  calves, 
chickens,  and  pigs,  and  these  animals  become  added  sources  of  income 
in  connection  with  the  dairy  industry. 


312  GENERAL  SCIENCE 

Exercises 

1.  Tell  what  difficulties  are  experienced  in  providing  and  distributing  an 

ample  supply  of  pure  milk  in  large  cities.     Why  is  it  that  milk  more  than 
other  foodstuffs  may  become  responsible  for  much  sickness? 

2.  What  constitute  sanitary  conditions  for  a  farm  dairy? 

3.  What  becomes  of  the  cows  found  unprofitable  for  dairy  use  because  of  age 
or  other  reasons? 

4.  In  what  respects  is  dairy  farming  as  a  life  occupation  (a)  rather  attractive; 

(b)  undesirable?     In  what  respects  is  there  less  of  drudgery  about  it  than 
formerly? 

5.  To  provide  an  ample  food  supply  the  year  around  for  his  cows,  and  to 

avoid  excessive  expenditures  for  ground  feed,  what  crops  may  the  dairy 
farmer  raise? 

6.  Name  several  important  considerations  that  largely  determine  whether  or 
not  a  region  is  well  adapted  for  dairying. 

7.  From  livestock  sold  and  shipped  to  distant  packing  houses  for  beef,  what 
is  the  farmer  as  a  consumer  likely  to  buy  back  eventually  in  one  form  or 
another?     Why  are  not  all  these  various  forms  of  foodstuffs  and  manu- 
factured products  prepared  in  the  home  community? 

8.  How  has  it  come  about  that  both  the  tanning  industry  and  the  manufac- 
ture of  shoes  are  carried  on  at  a  few  centres  only,  involving  as  this  does  the 
expenses  of  transportation  to  and  fro  of  the  raw  material  and  of  the  manu- 
factured product? 

9.  From  what  parts  of  the  world  are  there  importations  of  hides  and  beef? 
10.  What  has  caused  the  great  increase  in  creamery-made  butter,  and  the 

lessened  amount  of  the  "country-made"?     Aside  from  the  taste  given  to 
butter  by  salt,  what  purpose  is  there  in  its  use? 

LESSONS  ON  CORN 

To  travel  all  day  by  train  through  the  corn  fields  of  the 
Middle  West  at  a  time  when  the  crop  is  in  its  stage  of  most 
luxuriant  growth  gives  one  an  idea  of  bounty,  prosperity, 
and  promise  that  cannot  be  gained  by  any  reading  of  crop 
statistics.  The  development  of  the  agricultural  resources  of 
the  corn-growing  states  of  this  country,  and  their  growth  in 
population  and  wealth  within  a  half  century,  constitutes  a 
wonderfully  interesting  chapter  in  the  history  of  the  United 
States.  They  have  become  in  a  very  real  sense  the  granary 
of  the  nation. 


THE  FARM  313 

Corn  was  once  the  sole  crop  of  the  season  on  the  western 
farms  as  cotton  has  been  on  the  southern  plantations,  and 
there  was  an  accompanying  impoverishment  of  the  soil. 
Financial  distress  followed  from  crop  failures  and  from  low 
prices.  As  diversified  farming  has  replaced  this  practice 
more  and  more,  and  suitable  rotation  of  crops  has  taken  the 
place  of  a  one-crop  system,  improvement  in  agricultural 
conditions  has  been  marked. 


FIG.   101. — Corn  production  of  the  world.      (Robbins.) 

In  1916  the  world's  production  was  3,818,700,000  bushels.     (U.  S.  Department 

of  Agriculture.'} 


Need  of  conservation  of  the  fertility  of  soils  that  were 
formerly  regarded  as  inexhaustible  in  crop  capacity  has 
become  too  apparent  to  ignore.  It  has  been  found  that  by 
the  use  of  alfalfa  (or  other  plants  of  the  same  family  of 
legumes),  and  by  the  rotation  of  crops,  materials  for  plant 
food  are  restored  to  the  soil.  Through  the  agency  of 
" nitrogen-fixing"  bacteria,  soil  fertility  can  be  maintained 
in  a  degree  somewhat  comparable  with  the  improvement  of 
soils  in  the  dairy  districts  through  the  use  of  barnyard 
fertilizer. 

The   corn-growing  districts  of  the  world  are  limited  by 


314 


GENERAL  SCIENCE 


reason  of  climatic  conditions.  To  mature  the  crop  requires 
about  four  months  from  the  late  frosts  of  spring  to  the  early 
freezes  of  fall.  So  vigorous  is  the  growth  of  the  corn  plant 
that  abundance  of  water  and  of  plant  food  must  be  available. 
The  demand  for  moisture  is  especially  heavy  at  the  time 
when  the  ears  are  forming.  The  corn  plant  has  a  most  ex- 
tensive root  system  of  the  fibrous  form  penetrating  the  soil 
to  long  distances  in  all  directions.  In  the  growing  season  the 


FIG.   1 02. — Relation  of  corn  crop  (dotted  line)  to  rainfall  (solid  line). 


quantity  of  water  that  passes  from  the  leaves  into  the  air  by 
transpiration  demands  an  excessively  large  supply  daily 
from  the  soil.  To  conserve  the  moisture  content  of  the  soil 
requires  that  the  surface  layer  be  kept  finely  pulverized,  and 
that  the  ground  be  kept  free  from  weeds  which  rob  it  both 
of  moisture  and  of  food  material.  The  corn  plant  has  a 
relatively  large  amount  of  leaf  surface,  and  a  correspond- 
ingly large  amount  of  chlorophyll  by  means  of  which  the 
production  of  food  for  plant  growth  occurs. 


THE  FARM  315 

Corn  is  a  good  example  of  plants  bearing  two  kinds  of 
flowers.  Those  of  the  " tassel"  at  the  top  of  the  plant  have 
stamens  in  whose  anthers  an  abundance  of  pollen  is  produced. 
Lacking  the  part  of  the  flower  known  as  the  pistil  they  are 
staminate  flowers.  The  "silk"  of  the  corn  consists  of  unusu- 
ally long  styles  of  pistillate  flowers  at  whose  outer  ends 
are  the  stigmas.  At  the  inner  end  of  each  style  is  an 
ovule,  which  develops *  in  to  a!  grain  (kernel)  of  corn.  The 
corn  ear  is  a  mass  of  seeds  securely  enveloped  by  leaves 
(husks)  closely  crowded  together  upon  a  much  shortened 
stem. 

The  development  of  the  ear  and  the  consequent  production 
of  a  crop  of  corn  depends  upon  the  fertilization  of  the  ovules 
by  the  pollen  cells  that  fall  upon  the  stigmas.  Any  complete 
discussion  of  the  fertilization  of  flowers,  and  of  the  fascinat- 
ing teachings  of  plant  growth  and  reproduction,  requires  a 
study  of  Botany.  There  are  many  examples  of  pistillate 
flowers  on  one  plant  and  staminate  flowers  on  another.  This 
is  true  of  the  cottonwood,  poplar,  willow,  and  box-elder 
trees.  When  a  union  of  the  parts  from  the  pollen  and  the 
ovule  has  occurred,  there  results  a  new  cell  capable  of 
development  under  favorable  conditions  into  a  new  plant  of 
the  same  species.  The  seed  consists  of  this  new  plant  as  an 
embryo,  together  with  a  store  of  food  for  it  when  germination 
occurs  and  a  protective  covering  for  both. 

The  corn  depends  upon  the  wind  to  scatter  its  pollen  so  that 
every  ovule  may  be  fertilized,  and  the  ear  of  corn  have  no 
missing  kernels.  That  this  is  commonly  accomplished  is 
illustration  of  the  lavish  provision  of  nature  in  the  supply 
of  pollen.  A  large  amount  of  it  must  inevitably  be 
wasted.  Unfavorable  weather  conditions  at  the  time  when 
the  pollen  is  being  shed,  either  very  dry  and  hot,  or  a  long 
continued  rainy  period,  may  seriously  cut  short  the  crop  of 
corn. 


3i6  GENERAL  SCIENCE 

Whether  corn-raising  is  profitable  or  not  depends  upon  the 
cost  of  production  relative  to  the  market  value  of  the  crop 
produced.  To  increase  the  number  of  bushels  grown  per 
acre  on  the  farms  of  the  nation  without  any  corresponding 
increase  in  cost  of  production  adds  to  individual  and  national 
wealth.  The  agricultural  colleges  of  the  country  are  en- 
gaged in  experimental  work  to  this  end.  They  also  give 
courses  of  instruction  concerning  the  character  of  soils  and 
their  improvement,  the  nature  of  tillage  for  particular  crops, 
the  selection  and  advantageous  use  of  seed  in  crop  growing, 
the  cultivation  of  growing  crops,  and  the  manner  of  harvest 
and  storage  and  disposal  of  these  orops.  To  these  courses 
in  Soils,  Crops,  and  Farm  Management,  are  added  others  in 
Dairying,  Animal  Husbandry,  and  Horticulture,  thus  illus- 
trating the  diversity  of  interests  involved  in  general  agricul- 
ture. As  preparation  for  these  courses  there  is  need  of  some 
knowledge  of  high  school  Botany,  Chemistry,  Geography, 
and  Physics. 

The  list  of  uses  of  corn  is  a  long  one.  The  dry  stalks  with 
their  leaves  are  excellent  fodder  for  cattle.  Cut  into  short 
lengths  when  green,  the  whole  stalk  with  its  leaves  is  exten- 
sively used  for  filling  silos  to  furnish  feed  for  cattle,  especially 
on  dairy  farms.  Less  hay  is  needed  where  silage  is  provided, 
and  the  quantity  of  milk  from  dairy  cows  is  increased.  The 
corn  itself  (as  ground  feed  preferably)  may  be  worth  more  to 
the  farmer  when  converted  into  beef  and  pork  than  when 
marketed  as  corn. 

Bread,  cakes,  puddings,  and  hominy  are  appetizing  corn 
foods.  Corn  meal  by  reason  of  lack  in  gluten  requires  wheat 
or  rye  flour  mixed  with  it  in  making  corn  bread.  Corn 
starch  both  for  table  and  laundry  uses,  corn  syrup,  grape 
sugar,  and  corn  oil  are  all  extensively  manufactured.  Sweet 
corn  from  the  garden  and  in  cans  adds  variety  to  the  vege- 
table food  supply. 


THE  FARM  317 

SUMMARY 

Corn  can  be  raised  only  in  those  regions  where  the  growing  season  is 
four  months  or  more  free  from  frost.  Its  vigorous  growth  is  most 
noticeable  during  the  long  summer  days  of  hot  sunshine,  and  when  it  is 
warm  throughout  the  nights. 

The  demands  of  corn  upon  the  soil  for  moisture  are  very  heavy, 
especially  at  the  time  when  the  ears  are  forming.  So  wide  and  deep 
does  it  root  that  where  the  soil  was  thoroughly  prepared  in  the  spring, 
and  when  the  surface  is  kept  loose  and  free  of  weeds,  a  corn  crop  will 
stand  a  long  period  of  dry  weather  without  serious  harm. 

The  long  streamers  of  leaves  are  admirably  adapted  for  exposure  to 
sunlight,  and  for  absorption  of  large  amounts  of  carbon  dioxide  from 
the  air,  and  for  ridding  the  plant  by  transpiration  of  the  large  quantities 
of  water  required  in  its  growth.  The  so-called  veins  running  parallel 
and  lengthwise  of  the  leaves  are  a  continuation  of  woody  fibres  found 
in  the  stalk. 

The  corn  plant  bears  two  kinds  of  flowers.  The  ovules  after  being 
fertilized  become  kernels  of  corn,  and  they  are  arranged  along  a  short- 
ened stalk  or  cob.  The  pollen  is  so  abundant  that  under  all  ordinary 
conditions  every  ovule  is  fertilized,  and  there  are  no  kernels  lacking  on 
an  ear.  The  value  of  the  corn  crop  exceeds  that  of  any  other  product 
of  the  United  States. 

So  important  is  the  selection  of  seed  corn,  its  proper  care  till  planted, 
and  the  testing  of  it  for  its  power  to  germinate,  that  special  instruction 
is  given  in  all  these  details  in  agricultural  colleges.  By  careful  atten- 
tion to  improving  the  kind  of  corn  best  suited  to  any  region,  larger 
returns  per  acre  may  be  had  with  the  same  outlay.  This  is  a  matter 
of  profit  to  the  owner  of  the  crop,  and  an  increase  in  the  wealth  of  the 
nation. 

Starch  for  cooking  purposes,  and  for  laundry  uses,  is  made  in  enor- 
mous quantities  from  corn.  So  are  glucose  as  a  syrup  for  table  use, 
for  cooking,  and  for  confectionery,  and  grape  sugar  with  all  its  varied 
uses. 

One  variety  of  corn  when  well  popped  gives  delicious  and  wholesome 
eating.  Sweet  corn  in  season  has  much  use  as  a  vegetable  fresh  from 
the  garden,  and  as  green  (unripened)  corn  it  is  canned  in  enormous 
quantities. 

Exercises 

1.  What  is  the  meaning  of  the  term  "corn"  in  the  Bible? 

2.  What  is  the  first  that  is  known  of  maize,  or  Indian  corn?     Give  the 


GENERAL  SCIENCE 


THE  FARM  319 

Indian  legend  of  the  origin  of  maize  as  told  in  Hiawatha.  Tell  something 
of  corn  in  connection  with  the  history  of  the  early  settlements  in  this 
country. 

3.  Name  seven  of  the  greatest  corn-raising  states  of  the  United  States. 
What  portion  of  the  world's  supply  of  corn  (maize)  does  the  United 
States  produce?     Where  are  the  corn-raising  districts  of   the  world? 
Why  do  such  limitations  upon  its  production  exist? 

4.  At  what  season  of  growth  is  considerable  rainfall  indispensable  to  the 
corn  crop?     What  is  true  of  the  amount  of  sunshine  (clear  days)  required 
by  corn  as  a  crop? 

6.   What  kind  of  soil,  and  what  kind  of  land  surface,  favor  the  raising  of  corn 
on  an  extensive  scale? 

6.  Which  portion  of  the  kernel  is  relatively  rich  in  starch? 

7.  What  is  (a)  hasty  pudding;  (b)  hominy;  (c)  corn  syrup;  (d)  grape  sugar? 

8.  Name  several  of  the  forms  in  which  corn  is  put  on  the  market  as  a  food. 
Discuss  the  manner  of  preparation  of  some  one  of  the  "breakfast  foods" 
made  from  corn. 

9.  What  is  denatured  alcohol?     Why  is  it  denatured?     What  are  some  of  its 
uses? 

10.  Describe  a  scheme  for  testing  seed  corn  as  taken  from  the  ear.     Why  not 
use  corn  which  has  been  long  shelled  for  seed?     What  per  cent  should 
germinate  before  it  is  considered  good  enough  to  plant?     Why  test  corn 
at  all? 

11.  What  is  kaffir  corn?     How  is  it  unlike  maize? 

APPLE  RAISING  AS  AN  INDUSTRY 

When  at  a  fruit  stand  one  purchases  an  apple  to  eat  or 
orders  home  from  the  grocery  a  bushel  of  apples  for  family 
use,  there  is  occasion  to  wonder  why  this  product  of  farm  and 
orchard  in  a  large  part  of  the  United  States  should  be  so 
expensive  as  compared  with  the  cost  of  tropical  and  semi- 
tropical  fruits  shipped  in  from  more  distant  regions.  In 
the  earlier  history  of  this  country  apples  were  available  in 
most  homes  for  generous  use,  oftentimes  the  year  around. 
There  was  apple  sauce  and  baked  apples  for  the  table, 
together  with  apple  pies  and  apple  puddings.  From  bins 
and  barrels  in  cellar  and  cave  there  were  apples  to  eat  at 
all  times  in  accordance  with  one's  choice  in  flavor  and  in 
quality.  The  apple  in  some  one  or  more  of  its  many  uses 
as  food  formed  an  important  item  of  diet. 


GENERAL  SCIENCE 


. 


FIG.   104. — Apples  from  a  tree  unsprayed.     Only  those  in  the  basket  are  mar- 
ketable. 


FIG.  105. — Apples  from  a  tree  sprayed.     Those  not  marketable  are  in  the 

basket. 


THE  FARM 


321 


By  reason  of  the  codling  moth,  whose  larva  (lar'-ve) 
are  the  "  worms"  found  in  apples,  the  production  of  market- 
able apples  without  the  labor  and  expense  of  spraying 


FIG.   106. — Work  of  the  codling  moth. 


the  trees  several  times  in  a  season  is  almost  impossible. 
This  insect  pest  is  an  importation  from  the  apple-growing 
districts  of  Europe,  and  its  advent  has  caused  the  loss  of 
millions  of  dollars  annually  in  the  apple  crop  of  the  country. 


322  GENERAL  SCIENCE 

Many  of  the  old  time  orchards  have  been  allowed  to  go  to 
destruction,  given  over  to  the  ravages  of  worms  .and  to  such 
diseases  as  the  fungus  growth  called  " apple  scab."  For- 
merly every  home  had  its  apple  trees  about  the  house,  and 
every  farm  its  orchard.  Now  apple  raising  is  a  highly  spe- 
cialized industry  employing  a  large  investment  of  capital  and 
expensive  outfits  in  machinery  and  appliances.  It  demands 
much  business  ability  successfully  to  finance,  raise,  and  mar- 
ket the  crop.  m 

The  agricultural  colleges  of  the  country  have  done  much 
in  their  courses  in  horticulture  to  make  possible  the  success 
that  to-day  attends  the  effort  to  supply  again  to  the  American 
people  an  abundance  of  apples  as  a  most  wholesome  and 
appetizing  fruit.  To  fight  successfully  the  insect  pests  that 
attack  the  crops  of  the  farmer,  and  the  various  parasitic 
growths  like  the  apple  scab,  the  rust  on  wheat  and  oats, 
and  a  long  list  of  bacterial  diseases,  there  has  been  rapidly 
developed  the  need  of  a  scientific  education  in  agriculture 
as  an  occupation.  Biological  and  physical  sciences  as  applied 
in  agriculture  are  an  indispensable  preparation  for  success- 
ful farming.  Instruction  once  gained  only  through  expe- 
rience on  the  home  farm  is  now  given  as  courses  in 
college. 

The  material  used  as  a  spray  for  the  codling  moth  com- 
monly contains  some  compound  of  arsenic.  Paris  green  is 
often  used.  The  purpose  is  to  coat  both  the  leaves,  and  the 
fruit  (preferably  just  after  it  has  been  formed,  and  shortly 
after  the  blossoms  have  fallen)  with  a  fine  spray  of  the  poison- 
ous material.  The  larvae  hatched  from  eggs  laid  by  the 
moth  in  the  early  spring  are  killed  by  feeding  upon  the  foliage 
and  fruit.  Lime  when  slaked  is  a  fine  white  powder,  and 
when  mixed  with  the  water  containing  the  Paris  green  and 
applied  to  the  foliage  in  the  spray,  shows  by  its  whitening 
effect  just  how  evenly  and  completely  the  application  has 


THE  FARM 


323 


been  carried  out.     Any  material  for  the  purpose  of  destroy- 
ing insect  life  on  plants  is  known  as  an  insecticide. 

" Bordeaux  mixture,"  containing  copper  sulphate  along 
with  some  lime  in  the  water,  is  used  as  a  spray  for  the 
purpose  of  destroying  fungus  growths.  It  is  a  fungicide. 
To  apply  these  sprays  in  the  form  of  a  fine  mist  that  shall 
completely  cover  the  foliage,  twigs,  and  young  fruit,  requires 


FIG.   107. — Spraying   the   trees.     An    outfit    suitable   for    a    small    orchard' 

a  force  pump  operated  at  a  pressure  of  one  hundred  pounds 
or  more.  The  expense  of  equipment,  and  the  amount  of 
labor  required  to  keep  apple  trees  healthy  and  their  fruit 
fit  for  use  when  grown,  is  a  serious  handicap  in  fruit  growing 
on  a  small  scale. 

To  the  botanist  the  group  of  plants  known  as  the  fungi 
is  of  the  greatest  interest.  They  have  in  them  no  chloro- 
phyll for  the  manufacture  of  food  for  themselves.  They 
live  and  thrive  upon  what  they  appropriate  from  other 
plants  or  from  animals.  The  yeast  plant  is  a  fungus,  and 


324  GENERAL  SCIENCE 

so  are  the  moulds  that  grow  upon  foodstuffs,  and  the  rusts 
and  mildews  that  are  so  destructive  of  grain  crops.  They 
are  parasites  (see  page  40),  and  are  the  cause  of  losses  in 
agriculture  estimated  at  hundreds  of  millions  of  dollars 
annually. 

Bacteria  form  a  class  of  plants  closely  related  to  the  fungi. 
In  man's  struggle  for  existence  the  microscope  has  made 
possible  a  knowledge  of  these  hidden  agencies  which  have  so 
long  worked  havoc  with  his  food  supply,  with  his  health, 
and  with  life  itself.  In  the  field  of  agriculture  science  has 
scored  some  of  its  greatest  triumphs.  Intelligent  as  well  as 
persistent  efforts  are  necessary  in  order  to  be  assured  of 
success  in  a  never  ending  warfare  against  insects  and  plant 
diseases.  It  must  not  be  forgotten  that  in  this  warfare  the 
birds  are  man's  friends,  and  an  active  agency  in  the  destruc- 
tion of  insects. 

SUMMARY 

It  is  an  easy  matter  to  buy  and  set  out  apple  trees,  and  to  get  them 
to  grow  till  large  enough  to  bear.  But  there  is  occasion  to  wonder  why 
the  apples  growing  upon  them  are  so  poor  oftentimes,  and  the  trees 
so"  short  lived.  It  is  only  by  persistent  efforts  that  the  destruction 
wrought  by  the  codling  moth  can  be  combated  successfully.  Various 
fungus  growths  sap  the  strength  of  the  trees,  and  finally  kill  them. 

To  spray  successfully  trees  with  large  tops,  using  the  poisonous  com- 
pounds either  as  a  liquid  or  as  dust,  requires  a  powerful  force  pump, 
or  a  compressed  air  outfit.  To  move  the  equipment  and  the  materials 
used  from  tree  to  tree  through  an  orchard,  and  to  furnish  the  necessary 
labor  for  several  applications  every  season,  involves  much  expense. 
But  it  is  only  by  spraying  that  the  trees  and  their  fruit  can  be  saved. 

The  fungi  are  a  class  of  plants  wholly  destitute  of  chlorophyll,  and 
therefore  utterly  unable  to  prepare  food  for  themselves  from  the  raw 
materials  of  sap  water  from  the  ground  and  carbon  dioxide  from  the 
air.  As  parasites  the  fungi  thrive  by  living  upon  the  food  prepared  by 
other  plants  that  do  have  chlorophyll,  thus  robbing  those  other  plants 
and  possibly  in  time  starving  them  to  death.  The  annual  losses  in 
the  agricultural  productions  of  this  country -from  fungus  growths  on 


THE  FARM  325 

various  fruits  and  cereals  are  estimated  at  hundreds  of  millions  of 
dollars. 

Oranges,  lemons,  and  other  like  fruits,  have  rinds  that  protect  them 
from  the  bacteria  which  cause  decay.  But  the  skin  on  apples  is  thin 
and  easily  broken.  In  spite  of  a  wax-like  covering  that  in  some  apples 
is  quite  noticeable,  not  only  does  water  escape  through  the  skin  so  that 
the  apple  shrivels,  but  bacteria  penetrate  it  and  cause  rot.  When 
apples  have  been  carefully  selected  and  handled,  wrapping  them 
separately  in  paper  lessens  the  likelihood  of  their  decay. 


WHEAT  AND  WHEAT  GROWING 

So  common  has  been  the  use  of  wheat  flour  in  the  United 
States  that  it  is  difficult  to  readjust  the  manner  of  living 
when  compelled  to  do  without  it  either  wholly  or  in  part. 
So  widely  distributed  geographically  are  the  wheat-growing 
regions  of  the  earth,  and  such  is  the  range  of  climatic  con- 
ditions under  which  different  varieties  of  wheat  may  be 
grown  profitably,  that  a  world-wide  crop  failure  is  unlikely. 
But  it  is  quite  possible  under  normal  conditions  that  the 
world's  demand  for  wheat  may  increase  more  -rapidly  than 
any  increase  in  its  production,  resulting  in  a  rise  in  its  price, 
and  of  the  flour  made  from  it,  until  the  cost  of  wheat  bread 
is  prohibitive  for  many. 

Better  methods  of  wheat  culture  may  increase  the  average 
yield  per  acre  materially  through  better  tillage,  and  more 
careful  selection  of  seed.  It  is  possible  that  large  areas  of 
land  now  considered  unfit  for  wheat  growing,  especially  in 
the  semi-arid  regions,  may  be  brought  into  use  with  newly 
propagated  varieties  of  wheat  suited  to  these  unusual 
climatic  conditions.  It  is  possible  that  scientific  farming 
may  secure  increased  fertility  of  soils  in  spite  of  repeated 
croppings  with  wheat.  Any  gains  of  this  nature  are,  how- 
ever, likely  to  be  slow.  They  can  only  serve  to  delay  the 
coming  of  the  time  when  wheat  bread  with  butter  or  with 


326 


GENERAL  SCIENCE 


THE  FARM  327 

milk  shall  no  longer  serve  as  a  simple  and  well-balanced 
food  supply,  inexpensive  enough  to  come  within  the  means 
of  every  one  who  is  willing  to  work. 

With  the  development  immediately  following  the  Civil 
War  of  the  trans-Mississippi  region,  and  then  later  of  the 
great  Canadian  Northwest,  together  with  the  use  of  the 
wheat  lands  of  Australia  and  of  Argentina  in  South  America, 
the  wheat  supply  of  the  world  increased  much  faster  annually 
than  did  the  wheat-eating  population  of  the  world.  But 
there  are  no  longer  any  such  extensive  areas  of  fertile  soils 
waiting  the  plow  to  convert  them  into  wheat  lands  ready 
for  the  seeding. 

During  all  this  period  of  relatively  cheap  wheat  and  flour 
it  is  estimated  that  one- third  of  the  earth's  population 
has  subsisted  chiefly  upon  rice  as  a  cheaper  grain.  It  is 
owing  in  part,  also,  to  the  large  use  of  machinery  to  plow, 
to  reap  and  bind,  to  thresh  and  market  the  grain  econom- 
ically, so  far  as  labor  is  concerned,  that  the  prices  have  been 
maintained  at  so  low  a  level.  With  farm  lands  increasing 
in  value,  and  with  a  higher  price  for  labor  in  the  wheat- 
growing  districts,  there  is  an  increased  cost  of  production. 

The  need  of  labor  is  very  great  at  the  harvest  seasons. 
At  other  times  a  relatively  few  men  with  modern  outfits 
of  farm  machinery  can  give  the  necessary  care  to  the  largest 
wheat  farms.  This  condition  does  not  operate  to  distribute 
the  population  of  the  country,  nor  to  make  easy  the  problem 
of  bringing  together  the  work  that  needs  to  be  done  in 
agricultural  districts  and  the  men  who  are  seeking  work. 
Where  wheat  raising  can  be  carried  on  with  corn  growing, 
and  with  other  and  diversified  farm  interests,  the  require- 
ments for  labor  are  better  distributed  throughout  the  year, 
and  employment  is  given  to  more  persons  the  year 
around. 

The  large  per  cent  of  gluten  in  wheat  gives  it  a  food  value 


328  GENERAL  SCIENCE 

far  in  excess  of  corn  or  rice.  Gluten  is  a  protein  food  of 
great  worth  for  tissue  building.  It  is  the  gluten,  too,  that 
gives  to  flour  when  mixed  with  water  the  peculiar  consistency 
that  makes  possible  its  being  " raised"  into  the  familiar 
forms  seen  in  loaves  of  bread  and  cake.  When  once  raised, 
and  then  subjected  to  sufficient  heat  in  the  process  of  baking, 
the  loaf  retains  its  shape  by  reason  of  the  hardening  of 
the  gluten.  The  wheat  kernel  is  rich,  too,  in  those  mineral 
constituents  which  build  up  the  bones  of  the  human  body. 
These  compounds,  to  become  available  for  bone  building, 
must  be  dissolved.  Other  grains  less  extensively  grown 
than  wheat,  such  as  oats  and  rye,  are  also  rich  in  gluten  and 
in  mineral  content.  Rice  is  almost  wholly  a  starch  food, 
and  as  such  lacks  in  tissue-building  value. 

In  the  milling  process  it  is  possible  largely  to  eliminate 
the  gluten.  The  flour  is  somewhat  whiter  in  appearance 
and  makes  whiter  bread,  but  it  has  less  of  food  value.  The 
bone-building  value  is  likely  to  be  deficient  in  these  white 
flours.  From  the  big  flour  mills,  such  as  those  in  Minne- 
apolis, flour  is  shipped  to  all  parts  of  the  world.  The  daily 
output  of  one  mill  may  be  thousands  of  sacks.  The  outer 
part  of  the  kernel  as  separated  from  the  pulp  is  sold  as  feed 
for  farm  animals  under  the  name  of  bran.  The  mill  product 
known  as  " shorts"  contains  much  of  the  bran  along  with 
considerable  of  adhering  starchy  portions.  Dairymen  in 
the  past  have  bought  and  fed  to  their  cows  large  quantities 
of  both  bran  and  shorts.  Under  stress  of  war  conditions 
much  of  these  parts  of  the  wheat^are  retained  in  the  flour 
and  other  wheat  products  for  human  consumption.  The  old- 
time  grist-mill  has  largely  disappeared  from  rural  communities 
where  it  was  found  in  the  earlier  days.  In  the  great  wheat 
districts  the  crop  is  loaded  from  elevators  into  cars,  and 
railway  transportation  enters  into  the  problem  of  feeding 
the  millions  who  use  wheat. 


THE  FARM 


329 


SUMMARY 

The  leaves  of  the  wheat  plant  like  those  of  corn  are  lance-shaped  and 
parallel  veined,  and  at  their  base  form  a  sheath  about  the  stem.  The 
roots,  too,  are  fibrous  as  in  corn,  but  the  stems  are  hollow  rather  than 
filled  with  pith.  The  general  characteristics  are  such  as  to  class  the 
wheat  plant  among  the  grasses.  The  same  is  true  of  the  cereals  gen- 
erally. The  hollow  stem  of  the  grains  gives  a  maximum  of  strength 
for  the  amount  of  material  necessarily  provided  by  the  plant  in  the 
growth  of  the  straw. 

An  increase  in  the  wheat-growing  areas  of  the  world  through  develop- 
ment of  varieties  of  wheat  suited  to  regions  where  it  cannot  now  be 
grown  successfully;  an  increase  in  the  yield  per  acre  of  the  varieties  now 


LEADING    COUNTRIES 
/M  ACREAGE 


rr/LLIONS  OF  ACRE'S 

/f          JO  4S          60 


BUSHELS  PER  ACRE 


Russian  Empire  — 

United  States — 

/nd/a 

Argentina 

France  ._„ 

Austria    Hungary 

Italy . 

Canada 


FIG.  109. — Wheat  production  of  various  countries,  and  bushels  per  acre- 
In  1916  the  world  production  was  3,823,667,000  bushels.  (U.  S.  Department 
of  Agriculture.') 


raised;  and  the  maintenance  unimpaired  of  the  fertility  of  wheat- 
growing  soils,  are  problems  of  the  greatest  importance  in  feeding  the 
world's  population  now  and  in  the  future. 

While  other  cereals  such  as  rice  and  corn  are  rich  in  starch,  the  large 
content  of  protein  in  the  gluten  of  wheat  makes  all  the  wheat  foods 
especially  valuable  as  body  builders. 

On  the  great  wheat  farms  of  the  United  States  and  in  Canada  so 
much  of  the  labor  of  raising  the  crop  is  done  by  machinery  that  the  de- 
mand for  labor  is  small  except  at  harvest.  At  that  time  the  crop  must 
be  gathered  within  a  few  days'  time  to  prevent  loss.  Not  infrequently 
harvesting  goes  on  during  moonlit  nights.  The  extra  help  needed  dur- 
ing the  harvest  must  at  other  times  of  the  year  find  employment  else- 
where. Diversified  farming  on  the  other  hand  provides  employment 
for  laborers  the  year  around. 


330  GENERAL  SCIENCE 

Exercises 

1.  Name  the  chief  wheat-growing  states  of  this  country.     In  what  parts 
of  the  United  States  is  wheat  not  largely  grown?     What  apparent  reasons 
for  this  difference  in  crop  interests?     Compare  conditions  for  corn  and 
wheat  raising  as  to  (a)  climate;  (6)  character  of  soil. 

2.  Name  in  order  of  production  the  wheat-growing  countries  of  the  world. 

3.  Why  is  it  that  wheat  is  not  grown  more  extensively?     What  possible 
substitutes  are  there  for  wheat  in  the  feeding  of  people? 

4.  What  are   the  earliest   records  of   wheat  raising?     When   was   wheat 
introduced  into  this  country? 

6.   Name  several  kinds  of  breakfast  foods  wholly  or  largely  made  of  wheat. 


FIG.   no. — Percentage  of  the  wheat  crop  of  the  world  (1915)  grown  in  differ- 
ent countries.      (Robbins.) 

6.  What  period  of  time  under  favorable  circumstances  is  required  for  the 
germination  of  wheat? 

7.  Upon  what  does  the  market  price  of  wheat  largely  depend  aside  from  the 
cost  of  production? 

8.  At  what  times  in  the  year  does  the  wheat  crop  require  most  labor?     What 
attention  is  given  it  at  other  times?     How  does  the  labor  required  com- 
pare with  that  bestowed  upon  a  corn  crop  ?     What  labor  conditions  neces- 
sarily exist  in  wheat-growing  sections? 

9.  What  variety  of  wheat  is  most  largely  grown  in  your  section  of  country? 
Name  some  other  varieties.     Give  their  respective  merits,  and  any  spe- 
cial conditions  necessary  to  their  growth.     What  is  meant  by  "hybridi- 
zation" in  plant  growth? 

10.  Describe  in  detail  (a)  the  preparation  of  land  for  wheat  raising;  (b)  the 
methods  of  seeding;  (c)  any  cultivation  or  other  care  of  the  crop  till  har- 
vest; (d)  the  harvesting  of  the  wheat. 


THE  FARM 


331 


11.  What  were  the  early  methods  of  wheat  harvesting?     What  has  been  the 
effect  of  harvesting  machinery  (a)  on  the  labor  required  to  raise  wheat;  (b) 
on  the  cost  per  bushel? 

12.  How  much  wheat  is  used  per  acre  as  seed?     How  deep  is  it  put  into  the 
ground?     When  is  wheat  fit  for  harvesting? 

13.  Describe  early  methods  of  threshing?     What  advantages  are  there  from 
threshing  in  the  field  immediately  after  harvest?     In  what  sections  only 
can  this  practice  be  followed?     What  are  several  purposes  in  stacking 
wheat  or  in  housing  it  in  barns  before  threshing?     W7hat  is  the  "chaff" 
when  wheat  is  threshed? 


FIG.   in. — Cutting  and  binding  wheat  in  the  old  way. 


14.  What  is  the  range  in  yield  of  wheat  per  acre  in  the  United  States?     At 
eighty  cents  per  bushel,  what  value  is  represented  in  the  900  million 
bushels  of  the  1 9 1 4  wheat  crop  ?     Allowing  six  bushels  per  person  for  home 
consumption  in  the  United  States,  what  was  the  excess  for  export? 

15.  Describe  the  various  steps  in  making  wheat  flour.     What  is  meant  by 
the  "bolting"  of  flour? 

16.  In  milling  wheat,  about  what  per  cent  is  separated  as  bran?     How  does 
bran  differ  from  shorts?     What  is  "whole  wheat  flour,"  and  how  does  it 
differ  from  graham  flour?     What  is  "self-raising"  flour? 


332  GENERAL  SCIENCE 

17.  Of  what  nature  is  the  "rust"  on  wheat?  What  harm  results  from  it? 
What  is  meant  by  parasitic  plants?  What  course  may  be  pursued  to  save 
wheat  from  rust?  What  treatment  of  seed  wheat  may  be  employed  to 
lessen  "smut?" 

ORIGIN  AND  NATURE  or  SOILS 

To  the  careless  and  indifferent  mind  the  term  soil  may  have 
little  significance.  As  dust  it  gets  into  our  eyes,  and  it  makes 
the  life  of  the  house-keeper  a  burden.  As  mud  it  clings  to 
one's  shoes,  and  it  makes  travel  and  transportation  by  high- 
ways both  irksome  and  expensive.  To  the  botanist,  how- 
ever, soil  is  the  source  whence  the  higher  types  of  plants  get 
their  food  material  in  large  part,  and  in  which  the  mightiest 
oak  and  the  tiniest  violet  alike  find  root.  To  the  zoologist 
it  is  the  abode  of  innumerable  forms  of  animal  life.  To  the 
farmer  engaged  in  raising  crops  the  depth,  the  texture,  and 
the  chemical  nature  of  the  soil  tilled  by  him  is  of  utmost 
importance.  He  must  have  knowledge  of  the  kind  of  crops 
likely  to  be  most  productive.  He  must  learn  ways  of  con- 
serving the  fertility  of  the  soil,  and  of  managing  it  most 
profitably.  Courses  in  agricultural  colleges  involving  a 
study  of  the  origin  of  soils,  their  waste  and  restoration,  their 
characteristics  and  management,  and  the  effect  upon  soil 
structure  of  plant  and  animal  life,  require  a  knowledge  of 
Chemistry,  Geology,  Physical  Geography,  and  Physics. 

In  an  attempt  to  classify  and  name  soils,  no  mere  descrip- 
tion can  take  the  place  of  actually  handling  some  well-chosen 
types,  and  of  learning  through  first-hand  acquaintance  to 
recognize  and  name  all  local  varieties  of  soil.  Very  largely 
soils  may  be  described  by  making  combinations  of  the  terms 
gravel,  sand,  clay,  and  loam,  along  with  descriptive  adjectives 
advisedly  chosen,  e.g.,  a  light  sandy  loam,  a  stiff  clay  soil. 
Silt  is  composed  almost  exclusively  of  very  fine  particles  of 
earthly  material  such  as  the  sediment  from  running  waters 
when  their  current  is  checked.  When  dry  it  crumbles  read- 


THE  FARM  333 

ily.  Clay  consists  largely  of  yet  finer  particles  that  rub 
between  the  fingers  when  dry  much  as  does  flour,  and  when 
wet  form  a  soft  plastic  mass  which  hardens  into  lumps  on 
becoming  dry.  A  loam  is  characterized  by  no  particular 
size  of  particles,  but  is  loose  and  friable  even  when  quite  wet. 

Running  water  as  an  agent  in  erosion  has  been  discussed  in 
a  preceding  lesson.  It  is  to  be  noted  here,  however,  that  in 
the  transportation  of  eroded  soils  there  is  accomplished  a 
sorting  of  material  according  to  fineness  which  results  in 
beds  of  sand  in  some  places,  a  mud  deposit  as  silt  in  another, 
and  clay  banks  elsewhere.  From  an  agricultural  point  of 
view  this  sorting  is  an  unfortunate  one  when  these  lands  come 
under  cultivation.  It  is  one  of  the  problems  of  scientific 
farming  to  know  how  best  to  modify  any  particular  soil  by 
the  addition  at  least  possible  outlay  in  time,  labor,  and 
capital  of  those  materials  which  improve  its  fertility,  struc- 
ture, and  conditions  for  tillage. 

Any  sample  of  soil  gathered  from  field,  garden,  or  roadside 
commonly  has  in  it  vegetable  matter  in  different  stages  of 
decay.  This  may  be  burned  out  by  keeping  a  weighed 
sample  of  the  soil  at  a  red  heat  for  some  time  in  an  open  iron 
or  porcelain  dish.  Any  loss  of  weight  due  to  this  treatment 
of  a  thoroughly  dry  soil  represents  the  amount  of  organic 
matter  of  both  animal  and  vegetable  nature  that  was  in  it. 
The  very  large  per  cent  of  the  soil  sample  remaining  is  the 
mineral  portion.  Rock  material  in  a  finely  divided  state 
constitutes  very  largely  the  "soil"  in  which  plants  root 
themselves.  From  it  they  obtain  the  water  and  all  other 
food  material  necessary  to  their  life  and  growth  except  carbon 
dioxide. 

Soils  have  been  formed  by  disintegration  of  the  rocky  crust 
of  the  earth,  a  process  that  has  been  going  on  for  all  the  ages. 
When  their  fertility  (crop  productiveness)  has  once  been 
wasted  it  is  restored  naturally  only  after  long  periods.  The 


334 


GENERAL  SCIENCE 


nature  of  these  soils,  aside  from  the  organic  matter  in  them 
and  the  material  in  the  rock  originally,  also  depends  upon 
the  chemical  changes  that  may  have  accompanied  or  fol- 
lowed the  disintegration  of  the  rocks. 

Water  is  perhaps  the  chief  agent  by  means  of  which  the 
rocks  have  been  broken  down  and  reduced  to  a  finely  divided 


* 


FIG.  112. — Stratified  rock,  the  origin  of  which  dates  back  to  a  time 
when  the  material  in  it  was  deposited  as  a  sediment  in  layers  originally 
horizontal. 

condition.  By  its  freezing  and  thawing,  by  its  solvent  action 
and  its  powers  of  erosion  when  in  motion,  even  the  hardest 
of  rocks  are  slowly  worn  away. 

Rocks  exposed  to  the  direct  rays  of  the  sun  on  mountain 
sides  are  subject  to  rapid  expansion  and  contraction  of  their 
surface  layers  due  to  daily  temperature  changes.  As  they 
crumble  the  fragments  are  blown  away,  or  are  washed  down 
the  slopes.  Carbon  dioxide  gas  in  solution,  and  waters 


THE  FARM  335 

strongly  alkaline,  have  rapid  solvent  action  upon  certain 
rock  materials,  accompanied  by  chemical  changes  that  con- 
tribute to  their  reduction.  Decaying  vegetation  in  the  soil 
yields  acids,  and  these  acting  on  the  rock  material  aid  in 
bringing  about  its  disintegration. 

The  rock  known  as  granite  contains  among  other  con- 
stituents the  minerals  feldspar  and  quartz  each  of  which  has  a 
definite  chemical  composition.  The  feldspar  when  it  is 
exposed  to  the  action  of  the  atmosphere  slowly  disintegrates, 
giving  rise  to  clay.  The  quartz  particles  as  sand  grains  may 
remain  mixed  with  the  clay  to  form  loam,  or  may  be  separated 
from  it  by  running  water  and  both  deposited  in  beds  sepa- 
rately as  sand  and  clay.  Vast  areas  of  soil  often  of  great 
depths  have  been  transported  by  the  action  of  streams  and 
laid  down  where  we  find  them.  In  these  soils  sometimes 
clay  predominates,  and  sometimes  sand. 

SUMMARY 

Rocks  are  a  mixture  of  various  chemical  compounds  such  as  quartz, 
feldspar,  hornblende,  gypsum,  and  "limestone".  The  rock  constituents 
of  definite  chemical  composition  are  called  minerals. 

It  may  be  supposed  that  originally  the  earth's  land  surface  was 
composed  of  rock  only.  By  reason  of  expansion  and  contraction  due 
to  temperature  changes,  by  the  expansion  ol  water  in  the  rock  crevices 
when  it  froze,  by  the  chemical  action  of  carbon  dioxide  in  the  air  com- 
bined with  water  as  carbonic  acid  (H2CO3),  and  by  various  other 
agencies,  this  rock  crust  became  broken  and  pulverized  giving  rise  to 
soils. 

So  long  as  it  remained  in  place  this  soil  covering  protected  the  rock 
below  from  further  weathering.  Running  water,  however,  trans- 
ported this  broken  rock  material  elsewhere,  and  deposited  it  in  enor- 
mous quantity  and  to  varying  depths  as  sand,  clay,  and  loam. 

Mixed  with  the  earthy  material  of  the  soil  is  more  or  less  of  vegetable 
material  in  all  stages  of  decay.  And  in  and  through  it,  especially  the 
surface  layers,  are  varied  forms  of  animal  and  plant  life  so  that  instead 
of  being  dead  inert  material  the  soil  commonly  may  be  considered  as 
teeming  with  life. 


XIV.  PHENOMENA  OF  LIGHT 

SHADOWS  AND  ECLIPSES 

The  illumination  in  front  of  the  headlight  of  a  locomotive 
or  of  an  automobile,  or  one  caused  by  some  powerful  search- 
light, is  a  familiar  sight.  The  effect  is  the  more  startling 
when  the  air  is  filled  with  minute  water  particles  at  times  of 
a  fog,  or  when  there  is  much  fine  dust  or  smoke  in  the  air. 
If  into  the  space  thus  strongly  lit  up  a  large  opaque  body 
enters,  there  will  be  a  region  of  shadow  extending  outward 
from  the  body  and  away  from  the  source  of  illumination. 
This  shadow  is  the  space  from  which  the  light  is  cut  off  by 
reason  of  the  opaque  body.  A  cross-section  of  this  shadow 
region  gives  a  form  or  outline  like  that  of  the  body.  If  a 
screen  is  placed  outward  beyond  the  opaque  body  to  receive 
the  shadow  form  (cross-section),  and  it  is  moved  further  and 
further  outward,  it  will  be  found  that  when  the  opaque  body 
is  larger  than  the  light-giving  body  the  shadow  reaches 
outward  indefinitely  far.  The  area  of  its  cross-section 
increases  all  the  time.  If  the  opaque  body  is  smaller  than 
the  light-giving  body,  the  cross-section  grows  smaller  and 
smaller,  and  the  umbra  of  the  shadow  has  a  definite  end. 

The  astronomer  thinks  of  a  body  belonging  to  the  solar 
system,  and  receiving  its  light  from  the  sun,  as  at  all  times 
having  on  the  side  opposite  the  sun  a  shadow  region  pro- 
jected outward  into  space.  The  shadow  of  any  planet 
always  accompanies  it  in  its  course  around  the  sun,  as  does 
the  shadow  of  any  satellite  in  its  course  around  a  planet. 
To  the  astronomer  an  eclipse  of  the  moon  is  simply  the 
passage  of  the  moon  into  the  shadow  of  the  earth.  In 

336 


THE  PHENOMENA  OF  LIGHT  337 

the  somewhat  indefinite  but  distinctly  circular  outline  of 
this  shadow  he  sees  confirmation  of  his  belief  that  the  form 
of  the  earth  is  spherical.  A  so-called  " solar"  eclipse  is  to 
him  the  result  of  the  moon  coming  between  the  observer 
and  the  sun.  The  shadow  of  the  moon  overspreads  him 
as  an  observer,  and  it  is  really  a  case  of  an  eclipse  of  the 
observer.  It  would  be  so  called  by  observers  elsewhere  than 
on  the  earth  itself.  In  those  somewhat  infrequent  occur- 
rences where  the  moon  comes  directly  in  line  between  sun 
and  earth,  the  astronomer  is  given  a  very  few  minutes  of 
time  when  the  sun's  disc  may  be  completely  covered  by  the 
moon.  He  then  has  an  opportunity  to  observe  through  the 
telescope  the  phenomena  of  the  sun's  atmosphere  as  it  extends 
far  out  into  regions  not  hidden  by  the  moon.  By  aid  of  the 
telescope  it  is  possible  to  get  photographs  of  these  appear- 
ances. The  description  of  what  is  seen  at  these  times  of  a 
total  eclipse  of  the  sun,  and  the  interpretation  of  this  as 
given  in  texts  on  astronomy,  makes  fascinating  reading. 
Some  knowledge  of  the  beliefs  of  astronomers  concerning 
the  universe,  and  of  the  basis  for  such  beliefs,  should  be 
included  in  the  schooling  of  all  persons. 

It  was  from  a  study  of  the  times  of  disappearance  of 
one  of  the  moons  of  Jupiter  which  suffers  eclipse  every  few 
days,  and  from  his  interpretation  of  what  these  signified, 
that  Roemer  calculated  the  velocity  of  light  as  about 
186,000  miles  per  second.  So  exact  are  the  calculations  of 
astronomers,  and  so  regular  are  the  movements  of  the  heav- 
enly bodies,  that  it  is  possible  to  state  (from  calculations) 
the  time  of  occurrence  of  any  eclipse  in  the  past  or  in  the 
future,  its  duration,  and  where  visible.  The  astronomer 
deals  with  distances  and  periods  of  time  too  great  to  be 
comprehended  readily.  But  so  exact  are  his  measurements, 
and  the  calculations  based  upon  them,  that  any  slight  depar- 
ture of  his  observations  from  calculated  results  leads  to 


338  GENERAL  SCIENCE 

search  for  some  unknown  cause  of  the  variation.  Neptune, 
one  of  the  eight  planets  of  the  family  of  the  sun  to  which 
our  earth  belongs,  was  located  (discovered)  by  astronomical 
calculations.  The  telescope  verified  its  existence  when 
the  instrument  was  directed  toward  that  part  of  the  heavens 
where  the  hitherto  unknown  planet  had  been  mathemati- 
cally located. 

SUMMARY 

A  shadow  is  the  space  from  which  light  is  more  or  less  completely 
shut  off  by  an  opaque  body.  It  extends  outward  from  the  body  on 
the  side  opposite  the  illumination.  The  forms  seen  on  screens  and 
walls,  and  commonly  called  shadows,  are  cross-sections  of  the  shadow 
region. 

An  eclipse  is  a  phenomenon  where  an  illuminated  body  darkens  or 
completely  disappears  by  reason  of  its  entering  the  shadow  of  another 
body.  An  eclipse  of  the  moon  occurs  when  by  reason  of  its  revolution 
it  comes  into  the  shadow  of  the  earth.  Astronomers  can  calculate  the 
times  of  occurrence  of  eclipses  with  the  greatest  accuracy. 

The  outer  portion  of  the  sun  is  an  atmosphere  of  gases  and  vapors 
thousands  of  miles  deep,  and  this  atmosphere  is  so  highly  heated  as  to 
be  luminous.  From  this  "solar  atmosphere"  light  and  heat  come  to 
the  earth.  In  it  are  found  in  gaseous  form  nearly  all  known  chemical 
elements. 

The  existence  of  non-luminous  bodies  far  out  in  space,  and  wholly 
invisible  because  they  are  non-luminous,  is  made  known  to  astronomers 
by  the  effect  they  have  upon  the  motions  of  bodies  which  can  be  seen. 
Where  the  actual  position  or  path  of  motion  of  a  luminous  body  differs 
materially  from  its  calculated  place,  astronomers  feel  justified  in 
asserting  the  existence  of  one  or  more  invisible  bodies  whose  pull  of 
gravitation  occasions  the  change  in  position  or  in  motion. 

IMAGES  BY  REFLECTION  IN  PLANE  MIRRORS 

For  a  satisfactory  understanding  of  the  common  phenom- 
ena of  image  formation  in  plane  mirrors  such  as  looking- 
glasses,  a  knowledge  of  the  theory  of  light  as  taught  in  Physics 
is  required.  Whatever  light  may  be  (page  344),  it  is  very 


THF  PHENOMENA  OF  LIGHT 


339 


evident  that  the  mirror  has  served  to  change  its  course,  and 
to  reflect  it  (throw  it  back)  into  the  eye  where  the  optic  nerve 
is  affected  and  sight  a's  a  sensation  results.  Studies  in 
Physiology  and  Psychology  as  well  as  Physics  have  to  do 
with  what  occurs  after  light  enters  the  eye,  but  it  is  the  study 
of  light  before  it  enters  the  eye  that  concerns  us  here. 

It  is  evident  that  the  location  of  the  image  in  a  plane  mirror 
is  determined  by  the  light  direction  after  reflection.  The 
image  as  an  apparent  reproduction 
of  the  object  is  found  to  be  located 
back  along  the  lines  of  light  that 
have  come  from  the  mirror  into 
the  eye.  No  matter  to  how  many 
different  eyes  (people)  this  re-  ^ 
fleeted  light  from  the  mirror  f !  \ 
comes,  it  appears  to  originate  in  !  ! 
an  image  of  the  real  object  that 
has  the  same  position  behind  the 
mirror  for  all  observers.  To 

FIG.   113.— An  image  of  any 
draw  Straight  lines  from  the  eyes  of     point  as  seen  in  a  plane  mirror 

all    observers    back    through    the 


mirror  to  any  Single  point  in    that     are  equidistant  from  the  mirror 
^i_        J.-L      v    T-.L        -L  •   i       surface,       and      corresponding 

image  means  that  the  light  which    points  in  both  are  in  the  same 


the     Corresponding     perpendicular  (normal)  to  that 
&     surface. 


originated    at 

point    of    the    object,   must  have 

been  incident  upon  all  parts  of  the  mirror  surface.     In  this 

way  only  could  it  be  reflected  to  all  observers  so  that  the 

image  of  the  point  is  at  one  and  the  same  place  for  all. 

The  complexity  of  this  conception  is  much  simplified  by 
conceiving  that  from  every  point  in  either  a  luminous  body,  or 
of  one  illuminated  (shining  by  reflected  light),  there  is  sent 
off  a  continuous  series  of  every  expanding  light  waves  whose 
form  is  that  of  hollow  concentric  spherical  shells.  Now  to 
represent  the  directions  in  which  such  waves  are  sent  out, 


340  GENERAL  SCIENCE 

lines  can  be  drawn  outward  in  all  directions  from  the  point 
of  origin  as  a  center.  There  will  be  as  many  of  them  as 
there  are  radii  (ra'-di-i)  from  the  center  of  any  sphere — an 
innumerable  number.  Wherever  any  one  of  these  lines 
comes  to  the  surface  of  the  mirror,  at  that  point  there  is  a 
change  of  direction.  The  incident  line  of  light  then  becomes 
a  line  of  reflected  light.  These  reflected  rays,  then,  are  as 
many  as  there  are  points  in  the  reflecting  surface. 

An  explanation  of  this  location  of  images  in  plane  mirrors 
may  be  given  by  diagrams.  Let  any  two  radial  lines  repre- 
senting rays  of  light  be  drawn  from  the  same  point  of  an 
object  (such  as  one  of  its  extremities)  to  points  on  a  line 
representing  a  mirror  surface1.  These  rays  or  directions 
after  the  reflection  will  still  be  diverging  lines.  If  they  both 
enter  the  eyes  of  any  one  observer,  the  apparent  source 
whence  they  both  seem  to  come  will  be  back  along  both  lines 
of  reflection,  and  at  the  point  of  the  apparent  intersection 
of  these  lines.  All  observers  getting  reflected  light  from  this 
same  point  of  origin  will  locate  in  like  manner  all  images  of 
it  at  the  same  image  point.  An  image  of  the  opposite  ex- 
tremity of  the  same  object  as  a  source  of  light  is  fixed  in  the 
same  way.  So  are  all  intermediate  points.  Any  observer 
getting  at  least  two  rays  of  light  from  every  point  on  the 
side  of  the  body  toward  the  mirror  will  locate  in  the  same 
way  the  image  of  every  one  of  these  points.  These  im- 
age points  will  have  the  same  order  of  arrangement  with  re- 
ference to  one  another  as  was  true  for  the  points  whence 
the  light  originated.  For  diagrams  in  the  class  room  the  im- 
ages of  the  two  extremities  of  an  object  only  are  located, 
and  the  parts  between  are  filled  in  without  construction  work. 

With  polished  surfaces  it  is  believed  that  the  effect  of  the 
mirror  is  simply  to  change  the  direction  of 'the  lines  or  rays 
of  light  at  the  mirror  surface,  their  directions  relative  to  one 

1  Preferable  these  points  should  be  close  together. 


THE  PHENOMENA  OF  LIGHT 


341 


another  remaining  the  same.  But  when  light  falls  upon 
unpolished  surfaces,  the  reflection  is  of  such  a  character  that 
the  reflected  rays  no  longer  maintain  the  same  relative  direc- 
tions to  one  another.  They  are  so  scattered  in  their  relative 
directions  as  to  make  image  formation  as  discussed  above 
impossible.  Reflection  of  this  sort  is  called  diffusion.  It 
is  to  diffused  light  that  we  owe  the  freedom  from  images  in  all 
smooth  surfaces  by  which  we  are  surrounded,  and  the  even- 
ness in  distribution  of  light  within  our  rooms  and  out  of 
doors. 


FIG.   1 14.— Diffusion  of  light  is  scattered  irregular  reflection  owing  to  rough- 
ness of  the  reflecting  surface.     (Tower,  Smith  &  Turton.) 

SUMMARY 

In  reflection  of  light  the  ether  waves  are  thrown  back  from  the  re- 
flecting surface  into  the  same  medium  whence  they  came.  But  a  change 
in  their  direction  due  to  their  passage  obliquely  from  one  medium  into 
another  of  different  density  is  known  as  refraction. 

An  image  is  an  apparent  reproduction  of  an  object.  This  appearance 
is  due  to  the  fact  that  the  light  which  originally  comes  from  the  object 
itself  enters  the  eye  in  a  direction  such  that  it  seems  to  originate  in  the 
image  position. 

The  image  of  any  point  of  an  object  is  at  the  place  of  intersection 
of  two  or  more  lines  of  light  from  that  point  after  they  have  been  re- 
flected or  refracted.  This  intersection  is  often  apparent  rather  than 
real  as  in  case  of  images  in  plane  mirrors.  All  these  image  points  have 
the  same  relative  position  to  one  another  as  do  the  corresponding  points 
in  the  object,  thus  reproducing  the  object  so  far  as  form  and  general 
appearance  goes. 

Where  light  is  reflected  from  surfaces  not  sufficiently  smooth,  the 
relative  directions  of  the  light  rays  is  not  the  same  after  reflection  as 


342  GENERAL  SCIENCE 

before.  This  phenomenon  is  known  as  diffusion,  or  diffused  reflection. 
No  images  are  formed  as  result  of  it. 

Some  of  these  image  positions  are  such  that  a  screen  placed  there 
will  show  the  image  upon  it.  One  could  lay  hold  of  the  image  by 
grasping  it  in  the  hand  if  it  were  only  something  tangible.  Such 
images  are  said  to  be  real.  Virtual  images  are  those  where  this  is 
impossible,  their  positions  being  apparent  and  not  real.  The  light 
does  not  even  get  where  the  virtual  image  seems  to  be. 

In  plane  mirrors  the  virtual  image  of  an  object  is  so  located  that 
every  point  in  the  image  is  as  far  back  of  the  reflecting  surface  as  the 
corresponding  point  of  the  object  is  in  front  of  it,  and  a  line  connecting 
these  two  points  forms  a  right  angle  with  the  mirror  surface. 

COLOR  PHENOMENA 

In  order  to  enjoy  the  natural  colorings  of  sky  and  cloud 
and  landscape,  and  the  marvelous  combinations  and  blend- 
ings  of  color  in  flowers  and  in  the  plumage  of  birds,  it  is 
neither  necessary  to  make  a  study  of  Physics  nor  to  under- 
stand the  theories  by  which  scientists  explain  color  phe- 
nomena. One  may  become  skilled  as  a  painter  of  land- 
scapes, of  historic  scenes,  or  of  portraits;  he  may  be  a 
master  in  the  art  of  dyeing,  and  produce  the  brilliancy 
and  variety  seen  in  the  various  fabrics,  and  at  the  same 
time  know  nothing  of  the  scientific  explanation  of  these 
color  effects.  But  the  explanations  of  the  nature  of  light  and 
color  as  given  in  Physics  simplify  what  otherwise  would  re- 
main an  inexplicable  and  bewildering  number  of  unrelated 
phenomena.  The  teachings  of  science  concerning  color  phe- 
nomena is  a  good  illustration  of  how  advancement  in  learn- 
ing by  individuals  and  by  mankind  in  general  becomes  pos- 
sible through  the  efforts  made  by  scientists  to  ascertain  the 
nature  and  meaning  of  the  various  phenomena  of  life. 

When  a  beam  of  sunlight  is  passed  through  a  glass  prism, 
and  into  a  room  from  which  all  other  light  has  been  excluded, 
it  is  possible  by  a  proper  adjustment  of  the  prism  to  get  on 
a  screen  or  a  white  wall  a  band  of  overlapping  colors  like 


THE  PHENOMENA  OF  LIGHT  343 

those  of  the  rainbow — the  so-called  solar  spectrum.  The 
screen  or  wall  serves  simply  to  intercept  and  throw  the 
" colors"  back  into  the  eyes  of  observers.  These  colors 
were  in  the  sunlight  that  passed  through  the  prism,  and  they 
were  changed  from  their  straight  line  direction  as  they  passed 
into  the  glass  and  again  still  further  as  they  emerged  from 
it.  This  change  in  direction  of  the  light  is  caused  by  change 
in  density  of  medium.  The  color  elements  contained  in 
sunlight  are  bent  unequally,  and  they  diverge  more  and  more 
the  farther  the  screen  is  away  from  the  prism.  This  makes 
the  spectrum  longer  and  longer  without  completely  sepa- 
rating the  colors,  or  preventing  their  blending  into  one 
another. 

If  now  in  the  path  of  the  emergent  ray  a  blue  glass  plate 
is  held,  it  is  the  blue  light  of  the  spectrum  only  (or  largely) 
that  gets  through  the  plate.  The  other  colors  are  almost 
wholly  absorbed  by  the  coloring  material  in  the  glass.  If 
a  piece  of  common  window  glass  is  used  all  the  colors  pass 
through  it,  while  with  red  glass  nearly  all  the  colors  but  red 
are  stopped  by  the  glass.  When  both  blue  and  red  plates 
are  put  in  the  emergent  beam  together,  none  of  the  colors 
appear  on  the  screen.  Each  of  the  plates  has  absorbed  the 
colored  light  which  the  other  let  pass.  By  choice  of  the 
proper  pigments  to  go  into  glass,  and  by  varying  their  pro- 
portions, beautiful  color  effects  indoors  may  be  obtained 
with  windows  by  combining  in  varied  patterns  glass  of 
different  colors.  We  say  that  glass  is  blue  or  red  or  any 
other  color  according  to  the  kind  (color)  of  the  light  it 
transmits. 

When  only  the  blue  light  of  the  spectrum  appears  on  the 
screen,  and  a  sheet  of  paper  (or  any  white  object)  is  held  in 
its  path,  the  paper  in  a  darkened  room  appears  blue.  But  if 
a  red  screen  be  used  instead  of  a  white  one,  it  looks  black 
as  result  of  absorption  of  the  blue  light.  There  is  then  lack 


344  GENERAL  SCIENCE 

of  light  to  be  reflected.  If  a  red  glass  be  used  in  the  spectrum 
beam,  any  blue  object  upon  which  the  red  light  falls  will 
appear  black,  and  a  white  body  as  a  screen  will  look  red  in 
the  red  light  which  falling  on  the  screen  suffers  reflection. 
Color  in  itself  is  just  a  light  phenomenon  due  to  the  kind 
of  light  affecting  the  eye.  Color  as  a  property  of  bodies  is 
determined  by  what  color  elements  of  any  incident  white 
light  are  reflected  from  it,  and  in  what  proportions.  Thus  it 
is  that  "selective  absorption"  accounts  largely  for  the 
colors  of  objects  round  about  us  with  all  their  wonderful 
variations.  An  object  is  said  to  be  white  when  it  reflects 
all  the  color  elements  of  the  white  light  incident  upon  it. 

Light  reflected  from  bluing  left  in  cotton  cloth,  combined 
with  the  yellowish  light  reflected  by  the  natural  coloring  material 
in  the  cotton  fibre,  causes  when  received  into  the  eye  quite 
the  same  color  sensation  as  does  sunlight  when  reflected 
from  a  white  wall.  It  is  an  illustration  of  what  is  meant  by 
' '  complementary  colors . ' ' 

The  theory  that  light  is  wave  motion  in  an  ether  medium 
explains  color  phenomena.  The  mathematical  accuracy 
of  the  theory  is  very  striking.  Briefly,  the  theory  for  color 
is  that  the  nerves  of  sight  seem  to  be  attuned  to  respond  to 
certain  very  definite  numbers  of  vibrations  per  second  coming 
to  them  as  " ether  waves".  The  eye  is  able  to  distinguish 
more  or  less  sharply  between  at  least  seven  different  sets 
of  these  vibration  rates — the  so-called  spectrum  colors. 
This  is  very  much  the  same  condition  for  the  eye  as  that 
which  enables  the  ear  to  distinguish  vibration  rates  coming 
to  it  through  the  air  or  other  material  medium  as  the  "tones" 
of  music.  The  richness  (quality)  of  any  sound  is  increased 
by  the  blending  of  certain  combinations  of  sound  waves  per 
second,  making  possible  all  the  variations  whereby  we 
are  enabled  to  distinguish  the  voices  of  our  friends  and 
acquaintances  wherever  heard.  In  like  manner  the  blend- 


THE  PHENOMENA  OF  LIGHT  345 

ing  of  ether  waves  of  different  frequency  (number  per  sec- 
ond) gives  rise  to  all  color  effects,  however  wide  their  range 
in  beauty  and  character.  The  waves  per  second  said  to  give 
rise  to  the  colors  of  the  spectrum  from  red  at  one  end  of  the 
scale  to  violet  at  the  other  extreme,  are  numbers  so  great  as 
to  be  incomprehensible.  This  does  not  in  any  way  make  the 
theory  less  tenable,  or  its  mathematical  relationships  less 
sure.  It  has  been  mathematically  demonstrated  that  when 
once  the  wave  theory  is  accepted  all  these  color  positions  in  a 
spectrum  follow  naturally.  Spectrum  analysis  in  Physics, 
in  Chemistry,  in  Astronomy,  and  in  the  arts  and  industries, 
with  its  arrangement  of  color  lines  in  order  of  refrangibility, 
makes  possible  a  knowledge  of  the  chemical  composition 
of  highly  heated  bodies  at  distances  as  great  as  that  of  the 
sun.  Even  the  stars,  at  distances  enormously  greater,  re- 
veal in  their  stellar  spectra,  something  of  their  composition 
and  of  their  motions. 

The  fact  that  the  solar  spectrum  not  only  contains  the 
different  colors  distinguishable  by  the  eye,  but  that  they 
blend  imperceptibly  into  one  another  in  order  of  wave 
frequency,  suggests  that  in  the  sunlight  there  are  all  lengths 
of  ether  waves1.  The  prism  serves  to  sort  out  and  group 
those  of  the  same  or  approximately  the  same  frequency. 
Not  only  does  light  from  different  sources  vary  in  the  num- 
ber of  the  color  elements  present,  but  it  varies  even  more  in 
the  proportions  in  which  these  are  blended. 

When  physicists  make  studies  of  the  solar  spectrum  in  a 
room  from  which  all  other  light  is  excluded,  they  find  that 
in  the  region  beyond  the  violet  end  there  is  evidence  of  the 
existence  of  ether  waves  of  greater  frequency  (shorter  wave- 
length) than  the  violet.  These  waves  are  of  too  great  fre- 

1  The  lengths  of  the  various  ether  waves  causing  color  sensations  is  calcu- 
lated by  dividing  the  velocity  of  light  (about  186,000  miles  per  second)  by  the 
number  of  waves  per  second  for  any  color. 


346  GENERAL  SCIENCE 

quency  for  the  eye  to  recognize.  Photographic  plates  put 
out  in  this  ultra-violet  region,  and  kept  wholly  screened  from 
any  light  (ether  waves  capable  of  affecting  the  eye),  suffer 
much  the  same  changes  as  when  exposed  to  sunlight.  In 
fact  the  best  part  of  sunlight  for  photographic  purposes  is  that 
of  the  violet  end  of  the  spectrum.  It  is  said  to  be  rich  in 
actinic  rays. 

At  the  other  end  of  the  spectrum,  and  beyond  the  red  of  the 
spectrum  sufficiently  far  to  be  in  a  region  destitute  of  light, 
delicate  thermal  (heat)  instruments  detect  the  existence  of 
long  ether  waves  (waves  of  lesser  frequency).  These  waves 
are  incapable  of  affecting  the  eye  to  produce  light  sensations, 
but  they  are  capable  of  heating  effects.  Not  only  are  there 
ether  waves  recognized  by  us  as  heat  and  light,  but  there  are 
electric  waves  propagated  through  space  which  are  inti- 
mately related  to  the  other  wave  motions.  Perhaps  the  best 
illustration  of  this  to-day  is  the  transmission  of  electric  sig- 
nals through  the  ether  medium  in  wireless  telegraphy. 
There  is  suggested  in  all  this  the  possibility  that  all  the  so- 
called  " forces,"  or  forms  of  energy,  transmitted  through 
space  without  dependence  upon  any  material  medium,  are 
closely  related  to  one  another  and  to  the  ether  as  a  medium 
of  transmission.  It  suggests,  too,  the  possibility  of  forces 
wholly  unknown  to  man  as  yet,  and  perhaps  never  to  become 
known  by  reason  of  lack  of  any  means  by  which  to  compre- 
hend them. 

SUMMARY 

Light  is  one  of  the  forms  of  energy,  and  is  capable  of  affecting  the 
eye  to  cause  sight  or  vision.  Without  eyesight  knowledge  of  the  exist- 
ence of  light  would  be  impossible.  At  the  same  time  light  exists 
whether  or  not  there  be  any  eye  to  receive  and  take  note  of  it.  The 
study  of  light  in  Physics  has  little  to  do  with  sight  as  a  sensation. 

The  accepted  theory  concerning  the  nature  of  light  supposes  the 
existence  of  a  medium  known  as  ether,  and  the  transmission  of  the 


THE  PHENOMENA  OF  LIGHT 


347 


light  energy  as  a  series  of  waves  in  this  medium.  The  number  of  these 
waves  per  second  (the  wave  frequency)  may  so  vary  as  to  give  rise  to 
all  manner  of  wave  lengths  entering  the  eye  from  a  luminous  body. 
The  eye,  however,  responds  to  only  a  relatively  narrow  range  of  these 
ether  impulses.  It  recognizes  but  seven  different  colors  or  color  groups 
in  the  solar  spectrum.  There  is  no  sharp  line  of  separation  of  these 
colors  from  one  another. 


FIG.  115. — Dispersion  of  light  as  it  enters  at  D,  and  again  as  it  leaves  a 
falling  raindrop  at  V'R'.  The  internal  reflection  of  this  light  at  RV  rather 
than  its  transmission  through  and  beyond  the  falling  drop  makes  possible  a 
rainbow  in  the  east  when  the  sun  is  in  the  west  in  late  afternoon.  (Tower, 
Smith  &  Turlon.) 

The  great  variety  in  colors  coming  from  bodies  results  from  the 
blending  of  different  wave  lengths  in  different  proportions,  giving  rise 
to  color  sensations  of  a  composite  character. 

It  is  quite  possible  that  there  are  other  forms  of  energy  transmitted 
through  the  ether  medium  unrecognized  by  man  because  of  a  lack  in 
his  own  body  of  any  "receiving  apparatus."  Advances  in  science  may, 
however,  succeed  in  arresting  and  so  transforming  any  such  forms 
that  their  existence  and  nature  will  become  apparent.  Wireless  teleg- 
raphy, and  the  use  of  the  dynamo  for  the  production  of  electric  cur- 
rents, are  illustrations  of  the  uses  made  by  inventors  of  the  discoveries 
of  scientists.  The  discovery  of  "X-rays"  and  of  radium,  and  the 


348  GENERAL  SCIENCE 

applications  already  made  of  these  advances  in  scientific  knowledge, 
suggest  that  much  is  yet  to  be  learned  about  forms  of  radiant  energy. 
If  objects  reflected  all  the  light  incident  upon  them  their  colorings 
would  be  wholly  dependent  upon  the  kind  of  light  that  came  to  them. 
However,  it  is  found  that  varied  proportions  of  the  different  wave 
lengths  are  absorbed  into  bodies  upon  which  they  fall  according  to  the 
material  in  the  bodies.  This  phenomenon,  known  as  selective  absorp- 
tion, results  in  color  waves  being  reflected  from  a  body  that  may  be 
entirely  unlike  those  which  fell  upon  it.  Color  then  in  some  cases 
actually  does  become  a  characteristic  of  bodies,  indicating  the  presence 
in  them  of  certain  kinds  of  matter. 

Exercises 

1.  In  the  formation  of  rainbows  where  must  the  dispersion  occur?     Explain 
how  it  is  that  the  dispersed  sunlight  gets  back  to  the  observer  from  the 
part  of  the  sky  where  the  bow  is. 

2.  Account   for  differences    in    color    of    the  adjacent  parts  of  petals  of 
flowers. 

3.  Why  are  upper  cloud  masses  of  an  advancing  thunderstorm  often  silvery 

white  in  appearance,  while  the  under  surfaces  of  the  same  clouds  may  be 
inky  black? 

4.  Distinguish  between  reflection,  transmission,   and  absorption  of  light. 

Since  ether  waves  may  be  transmitted  through  bodies,  what  must  be  true 
of  the  existence  of  an  ether  medium  within  them? 

6.  Why  are  heat  and  light  said  to  be  forms  of  energy?  By  what  means  are 
both  supposed  to  be  sent  on  (propagated)  through  space?  Distinguish 
between  sight  and  light. 


XV.  THE  EARTH  AS  A  PLANET 

DAY  AND  NIGHT,  AND  THE  EARTH'S  ROTATION 

It  is  not  strange  that  the  ancients  believed  the  earth  was 
the  center  around  which  the  sun,  moon,  and  stars  revolved, 
or  that  from  the  time  of  Ptolemy  (A.  D.  100-170)  to  Coper- 
nicus (1473-1543)  it  was  taught  that  the  earth  was  the 
centre  of  the  universe.  In  these  days  we  believe  that  the 
earth's  rotation  accounts  for  the  daily  round  of  the  heavenly 
bodies  as  they  rise,  pass  meridian,  and  set.  But  it  is  neces- 
sary to  make  a  more  or  less  conscious  effort  really  to  think 
in  terms  of  the  Copernican  rather  than  of  the  Ptolemaic 
teaching.  The  very  language  we  use  tends  to  preserve  the 
older  views.  We  say  that  the  sun  sets,  the  moon  rises,  etc., 
and  we  fail  to  devise  any  better  expression  of  our  meaning. 
It  is  not  wholly  a  misfortune,  however,  that  so  much  of 
mental  effort  has  to  be  made  to  distinguish  between  what  is 
real  and  what  is  apparent  in  the  phenomena  occasioned  by 
the  earth's  rotation.  In  the  study  of  Astronomy  there  are 
ever  recurring  demands  actually  to  "see"  (to  visualize)  mo- 
tions of  celestial  bodies  in  space  that  are  similar  to  those  of  the 
earth.  The  development  of  an  imagination  based  upon 
known  realities,  and  of  a  power  to  grasp  abstract  mathe- 
matical notions,  is  of  greatest  educational  importance. 

If  the  earth  as  a  spherical  body  were  to  become  fixed  in 
space  (to  stand  still),  then  for  an  observer  at  any  one  place 
all  objects  above  his  horizon  would  remain  in  sight  all  the 
time,  and  objects  below  that  horizon  would  always  be  hidden. 
In  case  the  observer  were  to  travel  about,  his  horizon  would 
change  with  the  place  of  observation.  New  bodies  would 
come  into  view  as  his  horizon  dipped  below  them  in  whatever 

349 


350  GENERAL  SCIENCE 

direction  he  advanced,  while  others  at  the  same  time  would 
be  passing  out  of  sight  below  the  opposite  horizon  (the  direc- 
tion from  which  the  observer  is  moving).  If,  on  the  other 
hand,  an  observer  remains  at  the  same  location,  and  is 
carried  round  and  round  by  reason  of  rotation  of  the  earth, 
the  same  phenomena  of  the  rising  and  setting  of  celestial 
bodies  is  experienced. 

Why  the  rate  of  the  earth's  rotation  is  what  it  is  must 
remain  unknown.  But  this  rate  is  uniform,  and  its  period 
for  one  rotation  is  the  natural  time  unit  known  as  a  day. 
The  rate  of  rotation  so  far  as  known  varies  for  the  different 
planets,  and  their  day  periods  differ  somewhat  from  ours. 

The  whole  of  the  earth's  surface  moves  on  together  in  its 
motion  around  the  axis.  Those  portions  at  and  near  the 
equator,  which  have  a  much  longer  circumference  to  be 
carried  through  in  the  same  time  of  rotation,  must  have  a 
correspondingly  greater  eastward  velocity.  Near  the  poles 
the  number  of  miles  through  which  any  position  on  the 
surface  must  be  carried  to  make  a  completed  round  of  motion 
is  less,  and  the  eastward  velocity  there  of  the  earth's  surface 
is  relatively  small. 

Because  of  the  earth's  spherical  form,  as  an  observer  travels 
northward  his  northern  horizon  dips  lower  and  lower.  The 
North  Star,  which  at  the  equator  is  approximately  upon  the 
horizon,  seems  to  rise  higher  and  higher  as  he  advances 
northward.  Its  altitude  (distance  above  horizon)  is  for  him 
all  the  time  the  same  as  his  distance  from  the  equator  (his 
latitude).  Both  the  altitude  of  the  star,  and  the  latitude 
of  the  observer,  are  expressed  in  degrees. 

SUMMARY 

The  rising  and  setting  of  the  sun,  moon,  and  stars  is  a  direct  result 
of  the  rotation  of  the  earth.  As  the  earth  in  its  rotation  carries  us  as 
observers  around  on  its  surface,  our  eastern  horizon  passes  star  after 


THE  EARTH  AS  A  PLANET  351 

star  in  turn  and  moves  on  beyond  them.  This  causes  them  to  seem 
to  rise  and  pass  across  the  sky.  In  due  time  our  western  horizon  passes 
them  shutting  them  from  our  sight,  and  we  say  that  they  have  "set." 

In  like  manner  the  earth's  rotation  brings  the  sun  above  the  horizon 
of  an  observer,  causes  it  to  pass  across  the  sky,  and  then  to  disappear 
from  view  as  the  western  horizon  passes  it.  Thus  day  and  night  as 
periods  in  which  the  sun  is  above  or  below  horizon  follow  each  other 
in  endless  succession,  and  will  continue  to  do  so  as  long  as  the  earth 
continues  to  rotate. 

Places  at  the  equator  are  carried  eastward  by  the  earth's  rotation 
at  the  rate  of  over  one  thousand  miles  per  hour.  This  velocity  lessens 
toward  the  poles  where  it  has  a  zero  value.  Directly  related  to  these 
rotation  rates  are  the  directions  of  the  great  atmospheric  and  oceanic 
currents. 

It  is  because  of  the  rotation  of  the  earth  that  we  have  a  basis  for  use 
of  the  terms  axis,  poles,  equator,  and  parallels  of  latitude  in  connection 
with  earth  studies. 


ROTATION  COMBINED  WITH  REVOLUTION,  AND 
CHANGES  IN  SEASONS 

It  is  difficult  for  one  who  lives  in  the  middle  latitudes  to 
realize  what  is  true  of  seasonal  changes  in  the  far  north  or  in 
the  Torrid  Zone.  Experiences  gained  through  travel  assist 
in  comprehending  them.  ,To  understand  the  revolution  of 
the  earth  about  the  sun,  whether  studied  in  Physical  Geog- 
raphy or  in  Astronomy,  requires  more  than  mere  reading 
about  it.  Long  sustained  observations  of  celestial  phe- 
nomena as  " studies  of  the  sky"  when  intelligently  pursued 
afford  a  good  basis  for  such  an  understanding. 

The  lessened  meridian  altitude  of  the  sun  at  noon-time, 
from  June  to  December,  and  the  consequent  increase  in 
obliquity  of  the  sun's  rays,  is  accompanied  by  lessened 
heating  effects  day  by  day.  But  the  lowest  temperatures  of 
the  season  occur  later  than  December  because  of  the  cumula- 
tive losses  in  solar  heating.  Accompanying  these  changes  are 
shortened  periods  of  sunshine  (shorter  "days"),  intensifying 


352  GENERAL  SCIENCE 

the  results  of  a  lessened  insolation  and  of  the  ever  increasing 
losses  of  heat  by  reflection  as  the  angle  of  obliquity  increases. 
The  daily  path  of  the  sun  rises  continually  higher  in  the 
heavens  from  December  to  June,  the  sun  rising  farther  and 
farther  north,  crossing  the  meridian  higher  and  higher  up 
from  the  south  point  of  horizon,  and  setting  farther  and 
farther  north.  This  makes  an  ever  enlarging  diurnal  circle 


b' 

FIG.  116. — Diurnal  circles  of  the  sun  at  different  seasons:  axa',  at  summer 
solstice  (June  21);  bzb',  winter  solstice  (December  21);  EyW,  vernal  and 
autumnal  equinoxes  (March  21,  and  September  21).  dd'  is  the  diurnal  circle 
of  a  star  which  for  an  observer  in  northern  latitudes  never  rises  nor  sets,  i.e., 
a  star  always  above  horizon. 

above  the  horizon,  and  longer  and  longer  daytimes.  Upon 
these  changes  in  obliquity  of  the  sun's  rays,  and  upon  the 
duration  of  the  periods  of  sunlight,  depends  the  changes  of 
seasons. 

These  changes  are  scarcely  considered  from  day  to  day, 
and  less  frequently  are  they  given  their  real  significance  in 
terms  of  the  revolution  of  the  earth  about  the  sun.  When 
one  looks  out  toward  the  sun  at  any  time,  it  is  difficult  to 
realize  that  the  distance  between  the  earth  and  the  sun  is 
approximately  the  enormous  value  of  93,000,000  miles. 
So  distant  is  the  sun  from  the  earth  that  of  the  heat  given  off 
by  the  sun  only  about  one  two-billionth  part  is  received  by  the 


THE  EARTH  AS  A  PLANET  353 

earth.  Yet  great  as  is  this  distance,  the  earth  in  six  months 
time  will  be  at  an  equal  distance  on  the  other  side  of  the  sun. 
In  other  words  the  earth  will  have  traveled  about  half  way 
around  in  its  orbit.  When  one  calculates  the  number  of  miles 
in  half  of  the  earth's  path  about  the  sun,  and  divides  the 
result  by  the  number  of  minutes  in  six  months  of  time,  it  is 
not  surprising  to  find  that  the  earth's  velocity  in  its  orbit  is 
about  one  thousand  miles  per  minute.  This  is  about  a 
thousand  times  faster  than  the  swiftest  express  train. 

In  this  revolution  of  the  earth  about  the  sun  it  must  be 
kept  in  mind  that  the  moon  accompanies  the  earth  in  its 
advance.  The  earth  is  at  all  times  in  rotation  as  it  moves  on, 
and  the  moon  is  all  the  time  revolving  about  the  earth  as  a 
centre.  Though  the  rate  at  which  the  earth  moves  varies 
considerably  in  different  parts  of  its  orbit,  the  time  period 
for  complete  revolutions  is  of  unvarying  length,  and  it 
constitutes  the  natural  time  unit  known  to  us  as  the  year. 
In  this  year  period  there  are  about  three  hundred  sixty-five 
and  one-fourth  days.  In  the  arrangement  of  days  into 
months  to  make  up  the  calendar  it  has  been  necessary  to  let 
every  fourth  year1  contain  366  days,  February  then  having  in 
these  "leap  years"  twenty-nine  days.  The  times  of  changes 
of  seasons  are  thus  made  to  occur  on  the  same  dates  every 
year.  The  periods  of  revolution  of  the  other  planets  or  their 
" years"  vary  widely,  depending  upon  their  distances  from 
the  sun.  Mercury,  the  innermost  of  them,  gets  around  in 
about  eighty-eight  of  our  days,  while  Jupiter  requires  twelve 
and  Neptune  one  hundred  sixty-five  of  our  years. 

SUMMARY 

The  paths  of  the  sun  across  the  sky  are  not  the  same  day  after  day. 
It  is  a  matter  of  common  observation  that  from  June  to  December  the 

1  An  exception  to  this  is  that  the  first  year  of  each  new  century  as  1800, 
1900,  2000,  etc.,  is  a  leap  year  only  when  divisible  by  four  hundred. 
23 


354  GENERAL  SCIENCE 

sun  rises  farther  and  farther  south  on  the  eastern  horizon,  is  lower  and 
lower  down  from  the  zenith  at  noontimes,  and  sets  farther  and  farther 
south  on  the  western  horizon.  From  December  to  June  these  changes 
are  in  reversed  order.  The  duration  of  the  sunlight  period,  i.e.,  the 
length  of  the  days1,  varies  with  these  changes. 

In  the  northern  hemisphere  the  longest  days  are  in  June  when  the 
sun's  path  across  the  sky  is  highest  up  toward  the  zenith,  and  the 
days  are  shortest  when  those  "diurnal  circles"  are  lowest  down  toward 
the  south.  This  is  due  to  the  progress  made  by  the  earth  in  its  revolu- 
tion about  the  sun.  The  observer  is  brought  into  new  positions  in  the 
earth's  orbit  day  by  day  from  which  to  look  out  toward  the  sun  as  the 
earth's  rotation  brings  him  around  on  the  daylight  side. 

Upon  the  duration  of  the  period  of  sunlight,  and  upon  the  obliquity 
of  the  sun's  rays  for  any  observer,  depends  the  amount  of  solar  heat 
received  by  him,  and  the  changes  of  seasons  for  that  locality. 

The  year  as  the  period  of  the  earth's  revolution,  and  the  day 
as  the  period  of  the  earth's  rotation,  are  natural  time  units  of  unchang- 
ing values.  It  is  true  that  the  earth's  velocity  in  different  parts  of  its 
orbit  varies,  but  the  length  of  the  year  period  does  not  change.  The 
earth  is  "on  time"  so  far  as  completion  of  its  journeys  of  revolution 
are  concerned. 

The  lengths  of  the  times  from  passage  of  the  centre  of  the  sun's  disc 
across  the  meridian  of  any  observer  till  it  is  next  on  meridian  vary  a 
little  at  different  times  of  year.  This  necessitates  the  use  of  an  imagi- 
nary day  known  as  the  "mean  solar  day."  Its  length  is  the  average  of 
the  lengths  of  all  the  solar  days  of  a  year.  Our  clocks  and  watches 
keep  mean  solar  time. 

Exercises 

1.  Why  do  we  experience  so  much  difficulty  in  realizing  the  fact  that  we  live 
upon  a  rotating  earth? 

2.  What  is  meant  by  (a)  horizon;  (b)  sunrise? 

3.  Since  the  daily  paths  of  the  stars  across  the  heavens,  i.e.,  their  diurnal 
circles,   result  from  the  earth's  rotation,  and  since  the  direction  of  the 
earth's  axis  is  at  all  times  parallel  to  itself  and  always  points  toward  the 
same  place  in  the  heavens,  what  must  be  true  of  the  relative  positions  of 
the  diurnal  circles  (a)  of  different  stars;  (b)  of  the  same  star? 

1  It  usually  is  possible  to  distinguish  from  the  context  whether  the  word 
"day"  has  reference  to  the  period  of  the  earth's  rotation  (24  hours),  or  to 
the  duration  of  daylight  (not  night-time). 


THE  EARTH  AS  A  PLANET  355 

4.  Distinguish  between  rotation  and  revolution  for  the  earth.     What  is 
meant  by  the  orbit  of  the  earth? 

5.  How  much  nearer  the  sun  is  the  earth  in  our  winter  season  than  in  summer 
time?     What  is  true  of  the  relative  lengths  of  the  times  of  revolution  of 
the  earth,  i.e.,  of  the  lengths  of  the  years?     What  does  this  argue  of  the 
averages  of  the  earth's  velocity  in  its  orbit,  and  of  the  extent  (length)  of 
that  orbit  year  by  year? 

6.  Why  are  those  circles  of  the  earth  known  as  the  Tropics  located  23^° 
on  either  side  of  the  earth's  equator  rather  than  some  other  distance? 

7.  Account  for  eclipses  (a)  of  the  moon;  (b)  of  the  sun. 

8.  The  diameter  of  the  earth  is  8000  miles;  of  the  sun  880,000  miles.     How 
many  times  greater  volume  has  the  sun1? 

9.  What  is  the  cause  of  the  varying  obliquity  of  the  sun's  rays  as  found  in  the 
lesson  on  Solar  Heating? 

THE  MOON,  AND  ITS  PHENOMENA 

It  is  in  the  changing  phases  of  the  moon,  and  in  its  varying 
angular  distances  from  the  sun,  that  we  can  actually  see  the 
revolution  of  one  celestial  body  about  another.  The  moon 
is  only  240,000  miles  from  the  earth,  a  small  distance  in  the 
scale  of  the  celestial  sphere.  In  its  revolution  about  the 
earth  the  moon  comes  in  between  earth  and  sun  (though 
seldom  in  a  direct  line),  and  moves  on  away  from  the  sun 
farther  and  farther  as  measured  in  degrees  along  the  curved 
background  of  the  sky.  When  it  is  on  the  side  of  the  earth 
opposite  the  sun,  and  180°  from  it,  an  observer  on  the  earth 
sees  the  side  of  the  moon  that  is  illuminated.  Then  as  the 
moon  continues  in  its  path  around  the  earth  it  approaches 
closer  and  closer  to  the  sun  as  seen  from  the  earth  till  once 
more  it  is  on  the  same  side  as  the  sun.  The  dark  side  of  the 
moon  is  then  toward  the  earth.  The  moon  has  no  light  (or 
heat)  of  its  own. 

There  is  an  abiding  satisfaction  in  being  able  definitely 
and  quickly  to  grasp  the  relationship  of  sun,  moon,  and 
earth  in  space  as  the  moon's  form  and  its  position  relative 
to  the  sun  are  noted.  It  makes  an  excellent  preparation  for 

1  The  volumes  of  spheres  are  to  each  other  as  the  cubes  of  their  diameters. 


356  GENERA  SCIENCE 

any  later  studies  in  Astronomy.  In  estimating  distances  in 
degrees  on  the  surface  of  the  sky,  it  is  helpful  to  remember 
that  from  the  south  point  of  the  horizon  to  either  east  or 
west  points,  or  to  the  zenith,  is  90°.  The  diameter  of  the 
full  moon  is  about  J^°,  and  the  distance  between  the 
"pointers"  in  the  bowl  of  the  "Big  Dipper",  by  means  of 
which  the  North  Star  is  readily  located,  is  about  5°. 

The  full  moon  is  always  on  the  side  of  the  earth  opposite 
the  sun.  In  winter-time  the  sun  rises  far  to  the  south  of  east, 
and  sets  far  to  the  south  of  west.  This  is  because  the  north 
pole  of  the  earth  is  then  tipped  away  from  the  direction  of 
the  sun.  It  follows  that  the  rising  of  the  full  moon  at  sunset 
will  be  far  northward  of  the  east  point  of  the  horizon.  By 
reason  of  the  earth 's  motion  of  rotation  the  diurnal  circle  of  the 
full  moon  then  will  be  high  up  in  the  heavens,  and  down  to  a 
point  of  setting  far  northward  of  the  west  point  of  the  hori- 
zon. This  occasions  the  long  and  very  bright  moon-lit 
nights  of  midwinter.  These  are  in  marked  contrast  with 
those  of  summer  when  the  path  of  a  full  moon  across  the 
heavens  is  much  lower  toward  the  south,  and  the  light  of 
the  moon  much  less  intense  because  of  the  greater  obliquity 
of  its  rays.  To  attempt  to  reason  out  what  must  be  true  of 
natural  phenomena  such  as  these  requires  always  the  check  of 
actual  observation  at  every  opportunity  till  one  is  assured 
that  his  conclusions  accord  with  the  facts.  Acquiring  a 
clear  understanding  of  the  phenomena  presented  in  the 
changing  positions  of  the  moon,  and  verifying  one's  concep- 
tions by  repeated  observations,  enables  one  to  catch  some- 
thing of  the  spirit  of  the  scientist  as  he  seeks  to  master  what 
has  hitherto  been  unknown. 

In  many  respects  the  moon  itself  is  an  uninteresting  sub- 
ject for  study.  Astronomers  have  been  unable  to  detect  any 
evidences  of  life  upon  it,  or  to  note  there  the  physical  condi- 
tions essential  to  life  like  that  known  here  on  the  earth. 


THE  EARTH  AS  A  PLANET 


357 


There  is  no  atmosphere,  no  water,  no  protection  from  the 
intense  solar  heating.  For  two  weeks  at  a  time  the  sun 
shines  continuously  on  the  same  places.  There  are  no 
clouds  in  the  sky  to  prevent  radiation  of  this  heat,  and  it  must 
become  extremely  cold  through  the  two  weeks  of  continuous 
absence  of  sunshine  that  follows.  A  lunar  landscape  lit  up 


FIG.  117. — A  portion  of  the  moon's  surface  as  seen  in  a  telescope.  Note 
the  shadows  cast  by  mountains,  and  others  within  the  craters  of  lunar  vol- 
canos  now  extinct.  The  sunlight  is  from  the  left  side. 

by  the  sun's  rays  in  such  a  way  as  to  throw  into  shadow 
reliefs  the  rugged  mountainous  surface  of  the  moon  is,  how- 
ever, a  most  interesting  sight  when  viewed  through  a  good 
telescope.  Photographs  of  the  moon's  surface  when  made  by 
aid  of  the  telescope  give  a  good  idea  of  what  the  astronomer 
beholds. 

Our  moon  has  a  diameter  of  about  two  thousand  miles,  or 
one-fourth  that  of  the  earth's  diameter.  Its  volume  then  is 
approximately  (J^)3  or  J^4  that  of  the  earth.  Its  weight, 
however,  as  calculated  by  astronomers  is  but  J^o  of  that 
of  the  earth,  showing  that  the  material  of  which  the  moon 


358  GENERAL  SCIENCE 

is  composed  has  less  density  than  the  earth.  How  it  is 
that  astronomers  calculate  the  masses  of  the  planets  and 
their  satellites,  their  volumes  and  their  relative  densities,  is 
exceedingly  interesting  to  those  who  have  considerable 
knowledge  of  mathematics.  While  the  earth  has  but  the 
one  satellite  or  moon,  Jupiter  has  nine,  and  Saturn  nine  or 
ten.  Some  of  these  have  been  discovered  only  within 
recent  years. 

SUMMARY 

In  the  changing  positions  of  the  moon  relative  to  the  direction  of  the 
sun  from  the  earth  we  can  actually  see  the  moon's  revolution  about 
the  earth.  This  change  in  distance  of  the  moon  from  the  sun  must  be 
measured  in  degrees  upon  the  curved  surface  of  the  sky. 

As  the  moon  moves  on  in  its  orbit  its  illuminated  side  as  lit  up  by 
the  sun  is  at  times  toward  the  earth.  It  then  appears  as  a  "full" 
moon  circular  in  outline.  At  other  times  the  dark  side  is  toward  the 
earth,  while  the  crescent  and  gibbous  phases  are  views  of  but  portions 
of  the  illuminated  spherical  surface.  The  change  in  extent  of  the  sun- 
lit side  visible  from  the  earth  varies  chiefly  by  reason  of  the  moon's 
changes  of  position  in  its  orbit. 

Lack  of  water  and  of  atmosphere,  and  a  probable  extreme  range  in 
temperature  from  a  time  of  two  weeks  of  continuous  sunshine  to  a  two 
weeks'  absence  of  sunlight,  makes  it  unlikely  that  any  forms  of  life 
such  as  are  known  here  on  earth  can  exist  on  the  moon. 

The  duration  of  the  hours  of  moonlight,  and  the  variation  in  its  in- 
tensity, depends  as  with  sunlight  upon  how  high  up  toward  the  zenith 
of  any  observer  the  diurnal  circles  of  the  moon  are.  In  this  northern 
hemisphere  it  is  in  the  winter  time  that  the  full  moons  "run  high"  in 
the  heavens,  and  long  bright  moonlight  nights  occur. 

While  the  crescent  moon  as  seen  in  the  west  at  sunset  is  to  the  east 
of  the  sun,  and  the  crescent  moon  seen  in  the  morning  before  sunrise 
is  to  the  west  of  the  sun,  it  does  not  follow  that  the  moon  has  passed 
the  sun  and  changed  sides  with  regard  to  the  sun.  Such  a  change 
does  occur  at  the  "dark  of  the  moon,"  and  just  before  "new  moon." 
In  the  former  case  what  has  occurred  is  that  the  waning  crescent  of 
the  "fourth  quarter"  is  coming  nearer  and  nearer  to  the  sun,  both  its 


THE  EARTH  AS  A  PLANET  359 

distance  and  its  direction  now  being  measured  from  the  opposite  edge  of 
the  surfs  disc. 

Easter  is  the  first  Sunday  following  the  first  full  moon  that  occurs 
next  after  the  Vernal  Equinox  (time  in  the  spring  when  the  days  and 
nights  are  equal). 

TIME,  AND  TIME-KEEPING,  AND  STANDARD  TIME 

Time-keeping  resolves  itself  into  a  choice  of  convenient 
units  as  subdivisions  of  natural  time  periods,  and  the  use  of 
devices  for  counting  and  registering  these  smaller  units 
with  an  unfailing  accuracy.  Since  the  time  of  Gal-i-le'-o 
(1564-1642)  use  of  the  vibration  periods  of  pendulums  (or 
those  of  coiled  springs  in  watches)  has  displaced  the  hour- 
glass and  other  devices  of  the  ancients  for  measuring  time. 
They  had  the  years  and  the  days  for  large  time  units  the  same 
as  we,  but  accuracy  in  the  measurement  of  smaller  time  units 
waited  upon  the  discovery  of  the  laws  of  the  pendulum. 

It  is  quite  indispensable  that  the  time-pieces  of  a  com- 
munity— its  homes,  shops,  factories,  mills,  and  schools — 
shall  be  so  set  and  regulated  that  they  show  at  all  times  the 
same  readings.  Railway  service  in  all  parts  of  any  section 
of  the  country  requires  the  same  time  standard  by  all  con- 
cerned in  its  administration,  and  travelers  must  adapt  their 
times  to  this  standard. 

Since  the  earth  rotates  through  360°  of  circumference  in 
twenty-four  hours,  its  rate  of  rotation  is  15°  per  hour.  Any 
place  1 5°  eastward  of  an  observer  has  noon  by  the  sun  (that 
instant  when  the  sun's  centre  is  on  the  meridian  of  the  place) 
just  one  hour  earlier  than  noon  with  the  observer,  or  four 
minutes  earlier  for  every  i°  of  distance.  Places  westward 
of  the  observer  have  their  meridians  come  to  and  pass  the 
sun  four  minutes  later  for  every  degree  farther  westward. 
Observers  living  east  and  west  of  one  another  will  have 
different  "local  time"  whether  their  time-pieces  are  kept 


360  GENERAL  SCIENCE 

with  it  or  not.  It  is  more  convenient,  and  in  all  ways  more 
practical,  for  all  the  people  in  any  certain  section  of  country 
to  have  all  time-pieces  read  twelve  o'clock  when  it  is  noon 
at  places  situated  on  some  one  geographical  meridian  chosen 
as  a  standard.  By  having  these  standard  meridians  15° 
apart  the  time-pieces  in  adjacent  time-belts  will  be  exactly 
one  hour  apart.  A  traveler  going  from  one  such  section  into 
another  will  change  his  watch  reading  just  one  hour  at  some 
convenient  or  established  place,  leaving  the  readings  of  the 
minutes  and  the  seconds  unchanged.  If  the  traveler  jour- 
neys eastward,  his  watch  is  set  ahead  an  hour  for  every  change 
from  one  time-belt  into  another  in  order  that  its  readings  may 
conform  to  the  time  of  the  belt  into  which  he  has  come.  In 
going  westward  the  watch  must  be  set  back  an  hour  each 
time. 

It  is  interesting  to  note  what  befalls  a  traveler  in  the 
matter  of  time-keeping  who  makes  long  journeys  east  or 
west  around  the  earth.  If  changes  of  one  hour  at  a  time  are 
made  from  time-belt  to  time-belt  as  discussed  above,  the 
watch  readings  will  conform  always  to  the  times  of  the 
places  where  the  traveler  may  come.  But  confusion  soon 
arises  as  to  what  day  in  the  week  it  is. 

The  day  period  from  noon  to  noon  (or  midnight  to  mid- 
night) is  lengthened  in  going  westward.  The  traveler  has 
need  to  set  his  watch  back  one  hour  for  every  15°  passed 
over,  and  while  the  time  at  the  place  whence  he  started 
might  show  one  whole  day  passed,  the  traveler's  watch  after 
being  set  back  shows  but  twenty- three  hours  passed.  He 
has  "lost"  an  hour.  To  travel  30°  westward  means  a  read- 
ing at  the  place  where  the  journey  began  two  hours  later 
than  at  the  place  where  the  traveler  then  is,  or  two  hours 
lost.  To  complete  the  360°  of  the  earth's  circumference 
and  the  twenty-four  changes  of  watch  that  this  requires 
involves  the  loss  of  one  whole  day.  In  other  words,  at  the 


THE  EARTH  AS  A  PLANET  361 

place  where  the  journey  began  there  has  been  recorded 
twenty-four  hours  or  a  whole  day  more  of  time  than  has  been 
counted  by  the  traveler  with  his  repeated  "setting  back" 
of  his  time-piece.  He  is  a  day  behind  the  calendar  upon  his 
return.  While  his  watch  reading  is  in  accord  with  the  time 
at  the  starting  place,  his  day  of  the  week  is  made  right  only 
by  passing  over  one  day  in  the  calendar.  If  his  return  is  on 
Tuesday  evening  by  his  reckoning,  then  he  must  consider 
the  next  day  Thursday.  As  a  matter  of  custom  this  jumping 
over  one  of  the  days  of  the  calendar  is  done  by  west  bound 
travelers  when  crossing  the  Pacific  Ocean,  and  when  near 
the  so-called  international  date  line. 

To  travel  eastward  involves  a  similar  series  of  changes 
and  adjustment  of  days.  But  in  this  case  the  watch  must 
be  set  ahead  an  hour  at  a  time,  and  at  the  international  date 
line  two  days  in  succession  have  the  same  name.  There 
has  been  a  day  gained  by  the  traveler,  and  his  calendar  is  a 
day  ahead  of  the  places  to  which  he  comes,  making  it  neces- 
sary to  live  one  of  his  days  over  again  so  far  as  the  name  of 
the  day  is  concerned. 

Each  new  day  upon  earth  may  be  considered  as  having  its 
beginning  at  this  international  date  line,  and  as  traveling 
around  the  earth  westward.  When  this  same  day  is  just  be- 
ginning at  places  on  that  side  of  the  date  line  to  reach  which 
the  day  "has  traveled  around  the  earth,"  it  is  twenty-four 
hours  old  on  the  beginning  side  of  the  line.  The  whole  earth 
will  then  be  covered  by  the  same  calendar  day.  But  at  that 
very  instant  the  next  succeeding  day  is  beginning  on  the 
"east  side"  of  this  imaginary  line  to  pass  on  in  turn  around 
the  earth,  while  the  preceding  day  is  growing  older  and 
finally  is  to  pass  off  from  earth  when  the  new  day  in  turn 
comes  to  the  "west  side"  of  the  date  line. 

It  is  not  so  strange  as  at  first  it  may  appear  that  news- 
papers, with  headlines  that  tell  of  startling  events  in  Europe 


362  GENERAL  SCIENCE 

or  the  Far  East,  are  on  sale  in  cities  of  the  United  States 
at  hours  in  the  day  earlier  than  these  events  are  said  to  have 
occurred.  Telegraphic  transmission  of  news  has  out-stripped 
the  earth's  rate  of  rotation,  and  the  differences  in  time  of 
the  continents  gives  ample  opportunity  for  publication  of  the 
news  apparently  "before  it  happened."  To  visualize  such 
conditions  as  these,  and  to  be  able  concisely  to  express  in 
detail  these  relationships  of  time-keeping  over  the  world, 
is  a  worthy  test  of  one's  ability  to  think  clearly  and  surely  to 
conclusions  based  upon  involved  data. 

SUMMARY 

The  calendar  as  a  system  for  time-keeping  makes  use  of  the  periods  of 
rotation  and  of  revolution  of  the  earth — the  day  and  the  year — as  un- 
changing time  units.  Shorter  units  are  obtained  by  an  arbitrary  divi- 
sion of  the  average  length  of  solar  days  into  hours,  minutes,  and  seconds. 

Pendulums  and  springs,  by  proper  adjustment  of  their  lengths,  may 
be  made  to  vibrate  at  an  unvarying  rate  of  once  per  second,  or  any 
other  short  period  desired.  By  means  of  wheelwork  the  number  of 
these  vibrations  can  be  shown  on  a  dial  as  so  many  hours,  minutes, 
and  seconds  past  noon  or  past  midnight. 

A  ready  means  of  remembering  the  relative  times  of  places  east  and 
west  of  one  another  is  to  recall  that  "east  clocks  are  fast  clocks,"  the 
noons  of  places  east  occurring  earlier  than  at  places  west  of  them. 

To  travel  west  with  the  sun  has  the  effect  of  lengthening  the  day  of  the 
traveler,  so  that  in  going  around  the  world  he  has  had  one  less  number 
of  days  in  that  period  of  travel  than  has  another  person  who  has  re- 
mained at  home.  The  traveler  has  "lost  a  day,"  and  somewhere  on 
his  journey  westward  must  drop  a  day  from  his  calendar.  In  journey- 
ing eastward  around  the  earth  the  traveler's  days  are  shortened  as  he 
goes  to  meet  the  sun,  and  as  the  result  he  has  gained  a  day  in  making  a 
journey  around  the  earth.  It  thus  becomes  necessary  somewhere  in 
the  journeying  to  have  in  succession  two  days  of  the  same  name,  i.e., 
to  set  his  calendar  back  a  whole  day. 

" Standard  time"  is  a  system  of  time-keeping  whereby  the  clock 
readings  throughout  a  whole  section  of  country  are  the  same  regardless 
of  the  actual  time  at  these  different  places  as  indicated  by  the  sun. 


THE  EARTH  AS  A  PLANET  363 

All  time-pieces  are  set  to  read  noon  throughout  the  time-belt  when 
only  the  places  on  a  certain  meridian  running  through  the  central 
portion  of  this  region  really  have  the  sun  on  meridian. 

While  in  theory  these  time-belts  are  seven  and  one-half  degrees  of 
longitude  in  width  on  both  sides  of  each  of  the  time  meridians,  as  a 
matter  of  fact  there  are  great  departures  from  any  such  arrangement 
to  conform  to  the  convenience  of  the  traveling  public. 

Sunrise  during  the  Spring  and  Summer  is  so  much  earlier  than  the 
hour  fixed  by  custom  for  starting  the  wheels  of  the  nation's  industries 
that  in  many  ways  it  is  advantageous  to  have  the  industrial  day  for 
people  generally  begin  at  six  o'clock  rather  than  at  seven  A.  M. 
This  makes  the  mid-day  meal  come  at  eleven  instead  of  twelve 
o'clock.  Many  difficulties,  both  civil  and  legal,  would  be  involved  in 
any  change  in  the  hours  established  by  custom  and  by  statute  for 
beginning  and  closing  the  varied  activities  of  life's  affairs.  Instead, 
a  "Daylight-Saving  Plan"  now  followed  in  the  United  States  and  in 
other  countries  decrees  that  at  a  certain  date  in  the  Spring  all  clocks 
shall  be  set  ahead  one  hour,  and  then  set  back  one  hour  at  a  fixed 
date  in  the  Fall. 

The  round  of  daily  activities  during  the  Spring  and  Fall  then 
actually  begin  one  hour  earlier  every  day  and  close  one  hour  earlier 
at  night  than  during  the  other  part  of  the  year.  But  the  times  as 
shown  by  the  clock  remain  the  same  the  year  around.  During  the 
Summer  under  this  plan  the  sun  is  yet  an  hour's  time  from  meridian 
when  the  clock  reads  noon.  People  order  their  ways  of  life  by  clock 
time  rather  than  by  sun  time. 


XVI.     THE  HEAVENS 

"The  heavens  declare  the  glory  of  God,  and  the  firmament  sheweth  his 
handiwork.  Day  unto  day  uttereth  speech,  and  night  unto  night  sheweth 
knowledge.  There  is  no  speech  nor  language  where  their  voice  is  not  heard". 

Ps.  XIX:  vv.  i,    2,    3. 

Poets  and  philosophers  in  all  ages  have  gained  inspiration 
as  they  have  contemplated  the  heavens,  and  striven  to  formu- 
late and  express  the  thoughts  of  the  Infinite  to  which  these 
studies  have  given  birth.  Early  literature  contains  number- 
less allusions  to  astronomical  myth  and  fact.  To  catch  the 
subtle  meaning  of  many  a  passage  of  literary  excellence  re- 
quires some  acquaintance  with  Astronomy.  A  knowledge 
of  high  school  physics  renders  comparatively  easy  the  read- 
ing of  books  on  general  astronomy. 

But  one  does  not  need  to  be  an  astronomer  in  order  to  know 
something  about  the  universe  outside  the  earth,  and  to  com- 
prehend something  of  the  significance  of  what  is  visible  to 
him  of  the  celestial  sphere  both  by  day  and  by  night. 

Not  only  may  a  person  become  more  appreciative  of  the 
beauty  of  the  sky  as  apparently  it  moves  in  ceaseless  round 
above  him,  but  some  definite  knowledge  of  what  is  seen 
enriches  and  stimulates  his  intellectual  life.  An  intimate 
knowledge  of  plant  growths  by  field  and  forest  and  stream 
makes  life  more  enjoyable  to  us;  intimate  acquaintances 
among  people  gives  pleasures  to  life  which  no  crowds  of  those 
unknown  to  us  and  to  whom  we  are  indifferent  can  give. 
So  an  acquaintanceship  " amongst  the  stars"  yields  an  ever- 
increasing  pleasure  as  the  years  go  by.  To  be  an  astronomer 
onfc  must  become  skilled  in  mathematics;  but  there  is  avail- 
able to  every  one  in  the  realm  of  Astronomy  a  vast  fund  of 

364 


THE  HEAVENS 


365 


quickening  non-mathematical  knowledge  of  an  elementary 
character. 

So  vast  are  the  values  for  time,  space,  and  size  in  the  celes- 
tial sphere,  values  that  approach  the  infinite  in  their  magni- 


FIG.   1 1 8. — Constellations  of  the  northern  heavens  always  above  horizon  in 
most  parts  of  the  United  States. 

tude,  that  the  human  mind  must  resort  to  comparisons 
involving  enormously  large  units  in  many  cases.  Only  a  few 
of  the  more  serviceable  of  these  numbers  need  be  remem- 
bered, and  these  only  as  approximate  values.  The  velocity 
of  light,  186,000  miles  per  second1,  serves  the  astronomer  as 
1  The  velocity  of  sound  is  only  a  little  more  than  one-fifth  mile  (noo  feet) 
per  second. 


366  GENERAL  SCIENCE 

a  convenient  substitute  for  a  yardstick.  This  velocity  of 
light  is  so  great  that  to  encircle  the  earth  (25,000  miles) 
it  would  require  but  one-seventh  of  a  second.  To  reach  the 
earth  from  the  moon  (240,000  miles)  light  requires  some- 
what more  than  one  and  one-fourth  seconds,  and  from 
the  sun  (93,000,000)  somewhat  more  than  eight  minutes 
(499  seconds).  It  is  interesting  to  compute  the  number  of 
miles  light  travels  in  one  year  in  view  of  the  fact  that  astrono- 
mers calculate  the  distances  of  the  stars  as  so  many  "light- 
years"  from  the  earth. 

From  the  star  believed  to  be  nearest  the  earth  we  are 
told  it  requires  light  more  than  four  years  to  reach  the  earth; 
from  Sirius  the  "Dog  Star"  that  is  so  conspicuous  in  the 
southern  sky  in  a  winter  evening  more  than  eight  years ; 
from  the  North  Star  about  forty-seven  years;  and  from  those 
stars  most  distant,  and  yet  visible  on  photographic  plates 
made  by  aid  of  the  telescope,  perhaps  many  hundreds  of 
years.  When  we  consider  that  a  star  whose  light  we  are 
still  getting — that  we  still  "see" — may  have  been  blotted  out 
of  existence  unnumbered  years  ago,  something  of  the  extent 
of  the  Universe  is  borne  in  upon  the  human  mind. 

The  number  of  the  stars,  while  not  at  all  a  "  countless 
multitude,"  is  nevertheless  so  great  as  to  cause  amazement 
when  we  think  of  them  as  light-giving  bodies  like  our  sun. 
The  number  visible  to  an  observer  with  the  naked  eye  only 
at  any  one  time  and  place  is  perhaps  less  than  .two  thousand, 
or  about  five  thousand  in  the  whole  heavens  since  many  just 
above  the  horizon  are  not  readily  seen.  But  the  number 
of  stars  that  may  be  counted  on  photographic  plates  of  the 
whole  heavens  as  made  by  use  of  the  largest  telescopes  is 
perhaps  several  hundred  millions.  In  an  exercise  of  the 
imagination  based  upon  such  facts  as  these,  and  that  is  at 
all  times  in  accord  with  facts,  there  is  developed  the  noblest 


THE  HEAVENS 


367 
"to  think  the 


powers  of  the  human  mind,  enabling  man 
thoughts  of  the  Almighty  after  Him." 

Perhaps  the  readiest  way  in  which  to  recall  at  any  time 
the  relative  distances  of  the  planets  from  the  sun  is  to  make 
use  of  the  following  device  known  as  Bode's  Law: 


Name 

Mer- 
cury 

Venus 

Earth 

Mars 

Aster- 
oids1 

Jupi- 
ter 

Saturn 

Uranus 

Nep- 
tune 

Symbol 

5 

9 

e 

<? 

It 

ft 

£ 

t 

3 

6 

12 

24 

4 

48 

4 
96 

4 
192 

4 
384 

IO)4 

7 

10 

16 

28 

52 

IOO 

196 

388 

Relative 

distances 

•4 

0.7 

I  .0 

1.6 

2.8 

5-2 

10.  O 

19.6 

38.8 

Assigning  93,000,000  miles  as  the  unit  distance  for  the 
earth,  the  distance  of  the  sun  from  any  one  of  the  other 
planets  is  readily  found  in  round  numbers  by  multiplying 
the  earth's  distance  by  the  number  given  in  the  bottom  row. 
A  marked  exception  exists  in  the  case  of  Neptune  where  the 
multiplier  used  must  be  30  rather  than  38.8. 

It  is  interesting  to  calculate  the  intensity  of  light  and  heat 
from  the  sun  upon  some  of  these  other  planets  relative  to  that 
received  by  the  earth.  The  intensity  of  light  and  heat  at 
Neptune,  thirty  times  more  distant  than  the  earth,  is  (Mo)2 
or  one  nine-hundredth  as  much,  while  on  Mercury  which  is 
only  Jfo  as  far  away  the  light  and  heat  intensity  is  (l%)2  or 
about  twice  as  great. 


1  The  asteroids  are  small  planetary  bodies  revolving  about  the  sun  at  dis- 
tances approximately  as  indicated.  They  may  be  considered  as  fragments  of 
a  planet  which  for  some  unknown  reason  either  failed  to  unite  or  to  remain 
united  as  did  the  other  eight  planets. 


368 


GENERAL  SCIENCE 


The  table  below  gives  for  purposes  of  comparison  the 
diameters  of  the  eight  planets,  and  the  times  required  by 
them  for  one  revolution  about  the  sun  (their  year  periods) : 


9 

9 

e 

$ 

H 

fc 

$ 

\ 

Diameter  (in  miles)  

3,000 

7,700 

7,920 

4,200 

88,000 

75,000 

31,700 

34,5oo 

Times  of  revolution  

88 

225 

365 

687 

n% 

29% 

84 

165 

days 

days 

days 

days 

years 

years 

years 

years 

The  astronomer  considers  our  sun  as  a  star,  and  the  stars  as 
so  many  suns.  The  little  heat  and  light  received  on  the 
earth  from  the  stars  results  from  their  enormous  distances. 
Many  of  them  must  be  vastly  larger  than  our  sun.  If  any 
of  them  have  planets  circling  about  them,  these  planets 
must  remain  invisible  because  of  the  distances  involved 
(page  366).  Even  from  Neptune  the  light  is  too  feeble  to  be 
made  out  by  the  naked  eye,  although  it  is  approximately 
only  thirty  times  the  sun's  distance  from  the  earth,  and 
consequently  is  but  30  X  499  light-seconds  (or  4  light-hours) 
away  as  contrasted  with  4  light-years  for  the  nearest  star. 

Astronomers  believe,  too,  tiiat  our  sun  with  all  its  attend- 
ant planets,  asteroids,  and  satellites,  is  moving  onward 
through  space  more  or  less  free  of  the  controlling  influence  of 
other  celestial  bodies.  This  independence  in  motion  is  true 
of  all  the  stars,  but  so  vast  are  the  celestial  spaces  that  colli- 
sions, though  possible  in  long  periods  of  time,  are  unlikely. 
The  theories  given  in  Astronomy  of  the  structure  of  the 
Universe,  as  well  as  of  the  origin  of  our  Solar  System,  merit 
the  thoughtful  consideration  of  all  students. 

SUMMARY 

So  distant  are  many  of  the  stars  that  their  light  is  too  faint  to  affect 
the  eye  sufficiently  for  them  to  be  seen.  The  great  telescopes  are  as  it 
were  enlarged  eyes,  gathering  up  a  far  greater  amount  of  light  than 


THE  HEAVENS  369 

does  the  unaided  eye.  Photographic  plates  made  in  connection  with 
use  of  the  telescope  multiply  enormously  the  stars  that  can  be  num- 
bered. There  is  reason  to  believe,  however,  that  the  number  of  the 
stars  is  not  limitless. 

Bode's  so-called  "law"  probably  has  no  value  other  than  as  a  device 
for  making  an  easy  calculation  of  the  distances  of  different  planets 
from  the  sun.  It  is  to  be  noted  that  the  number  to  be  added  to  each  of 
the  four's  is  in  every  case  double  the  preceding  number. 

The  existence  of  so  many  non-luminous  companions  of  the  stars  has 
been  established  that  it  is  not  unreasonable  to  conceive  that  at  least 
some  of  the  stars  are  centres  of  solar  systems  even  as  our  own  sun  is. 
However,  astronomers  lack  sufficient  evidence  to  warrant  any  such 
assertion.  The  human  mind  naturally  wonders  if  in  all  the  immensity 
of  space,  and  out  of  all  the  multitude  of  celestial  bodies  corresponding 
to  what  we  know  as  satellites,  planets,  and  sun,  our  earth  alone  is  in- 
habited by  intelligent  beings  like  ourselves. 

Scientists  are  very  careful  to  avoid  teachings  that  lack  sufficient 
evidence  in  known  facts  to  warrant  their  acceptance.  On  the  other 
hand,  imagination  based  upon  facts,  and  tested  at  every  stage  so  far  as 
possible  by  what  is  known  to  be  true,  enables  the  human  mind  to 
compass  the  universe.  And  when  the  limit  of  human  knowledge  is 
reached,  as  so  quickly  it  is,  the  reverent  mind  readily  believes  that 
within  the  shadows  standeth  God  "  Keeping  watch  above  His  own." 


APPENDIX 

SUGGESTIONS  TO  TEACHERS 

A  good  " method"  for  any  subject  in  school,  and  for  the  affairs  of 
life  generally,  attains  the  ends  desired  with  a  minimum  of  waste  in 
time  and  effort.  In  school  work  the  teacher's  personality  and  prepara- 
tion, the  varied  experiences  and  natures  of  pupils,  and  the  different 
conditions  under  which  instruction  must  be  given,  all  enter  into  the 
teaching  problem  as  variable  factors.  Any  one  best  way  of  teaching 
a  secondary  school  science  is  out  of  question.  "Diversity  in  method 
but  unity  in  aim"  may  well  be  a  motto  for  science  teachers.  Never- 
theless, until  through  much  experience  a  science  teacher  establishes  a 
procedure  peculiarly  his  own,  yielding  better  results  than  any  other 
ways  employed,  it  is  well  to  follow  plans  found  satisfactory  by  others. 

In  his  own  class  work  the  author  seeks  to  keep  before  the  minds  of 
prospective  teachers  that  the  teaching  process  is  something  more  than 
a  mere  discussion  of  any  group  of  facts,  however  great  their  values  as 
knowledge  material.  It  is  of  primary  importance  that  pupils  be 
trained  to  acquire  facts  for  themselves,  and  that  they  become  able  to 
discriminate  in  the  relative  worth  of  these  facts.  A  natural  spirit  of 
inquiry  concerning  the  significance  of  nature's  ways  is  thus  stimulated 
and  directed. 

Teaching  conditions  will  commonly  make  necessary  the  use  of  a  text 
as  the  chief  source  of  information  for  pupils  since  it  gives  relationships 
of  greatest  educational  worth  likely  to  be  foreign  to  their  thought,  and 
conclusions  of  utmost  importance  not  likely  to  be  reached  by  them. 
But  it  is  the  author's  belief  that  large  emphasis  should  be  laid  upon 
laboratory  procedure  in  the  teaching  of  General  Science.  There  is  a 
wide  difference  in  educative  values  for  the  beginner  in  sciences  between 
what  he  learns  through  experiments  and  through  the  experiences  of 
life,  and  what  he  gets  from  books  alone.  To  make  beginning  work  in 
science  a  study  of  books  only  is  contrary  to  the  spirit  of  the  work,  and 
destructive  of  its  ends.  Later  in  the  school  course,  with  acquired 

370 


APPENDIX  371 

abilities  and  enlarged  powers  of  interpretation  of  language,  pupils  may 
be  turned  more  and  more  from  studies  of  natural  forms  and  phenomena 
to  what  is  told  about  them  in  books.  It  is  the  teacher's  problem  to 
know  when  and  how  rapidly  to  do  this. 

Laboratory  exercises  constitute  in  large  measure  a  preparation  for 
the  class  period.  Text  requirements  and  reference  readings  are  made 
supplementary  to  the  life  experiences  called  forth  by  the  laboratory 
requirements.  Whether  the  experiments  are  performed  by  the  indi- 
vidual pupil,  or  by  the  teacher  before  the  class  as  a  whole,  is  far  less 
important  than  is  an  insistent  demand  for  a  discernment  of  the  sig- 
nificant facts,  and  of  their  relationships  to  one  another  and  to  previous 
knowledge. 

It  is  to  be  noted  in  this  connection  that  the  pupils  are  to  do  the  ob- 
serving, and  to  the  limit  of  their  ability  are  to  be  required  to  interpret 
the  significance  of  what  comes  under  their  observation.  It  is  the 
province  of  the  teacher  to  direct  in  these  exercises,  to  guide  in  the  think- 
ing, to  aid  in  the  expression  of  thought  and  in  the  mastery  of  a  science 
vocabulary.  It  is  the  teacher,  too,  who  so  plans  and  executes  that 
results  of  largest  educational  value  are  secured  in  the  shortest  time 
and  in  the  most  direct  ways.  In  the  class  period  when  the  results  of 
the  laboratory  exercises  are  under  review,  there  is  opportunity  for  the 
teacher  to  bring  into  the  discussion  much  closely  related  matter  that 
is  unsuited  for  study  by  observation. 

It  is  at  this  stage  that  texts  and  other  books  for  supplementary  read- 
ing furnish  an  inexhaustible  wealth  of  information.  From  the  use  of 
these  the  pupils  may  acquire  a  more  extended  outlook,  and  may  satisfy 
a  growing  desire  for  more  definite  knowledge.  In  this  use  of  texts  and 
reference  material  there  is  relief,  too,  for  the  teacher  otherwise  over- 
burdened by  the  heavy  demands  of  instruction.  In  the  selection  and 
assignment  of  any  reference  readings  no  less  care  should  be  exercised 
with  regard  to  their  educational  worth,  and  their  adaptation  to  teaching 
ends,  than  in  the  choice  of  laboratory  exercises. 

Teaching  conditions  are  often  such  as  to  make  impossible  any  ex- 
tended use  of  reference  books  in  General  Science.  Provision  can 
always  be  made,  however,  for  individuals  to  do  much  outside  reading. 
The  field  of  General  Science  is  so  broad  that  no  one  book  is  at  all  ade- 
quate as  a  text.  Some  of  the  books  and  bulletins  listed  in  this  Appen- 
dix should  be  provided  for  supplementary  assignments,  and  the  teacher 
should  become  thoroughly  familiar  with  their  contents.  In  them  and 
in  other  like  books  a  wealth  of  valuable  information  may  be  turned  to 


372  GENERAL  SCIENCE 

good  account  in  general  science  teaching.  Pupils  should  learn  from 
the  first  to  use  the  Index  of  any  reference  book  for  finding  quickly 
what  is  desired  as  information.  Certain  of  the  chapters  of  this  text 
as  listed  in  the  Table  of  Contents  have  been  starred(*).  In  the  author's 
judgment  they  contain  matter  likely  to  be  difficult  for  beginners. 
Their  use  in  a  general  science  course  will  in  nowise  render  unnecessary 
their  more  extended  discussion  later  in  the  particular  science  to  which 
they  pertain,  especially  the  lessons  in  Physics  and  Chemistry.  An 
introduction  of  pupils  to  these  difficulties  at  this  early  stage  in  their 
science  studies  should  so  materially  aid  them  later  in  any  discussion 
of  these  same  and  of  other  related  topics  as  to  justify  the  inclusion  of 
these  lessons.  It  will  be  for  any  teacher  to  judge  whether  under  teaching 
conditions  as  they  exist  it  is  profitable  to  discuss  them. 

*      REFERENCE  BOOKS 

1.  Text-books  in  high  school  and  college  sciences  provide  a  large 
amount  of  usable  material  for  "study  hours"  in  General  Science. 
These  should  include  texts  in  Agriculture,  Astronomy,  Biology,  Geology, 
Home  Economics,  Hygiene,  Meteorology,  and  Zoology  as  well  as  in 
Botany,    Chemistry,   Physical   Geography,   Physics,   Physiology,  to- 
gether with  some  of  the  different  texts  in  General  Science.     A  simple, 
non-technical  presentation,  other  things  being  equal,  is  desirable1. 
Accuracy  of  information  is  essential  within  the  limits  of  discussions 
necessarily  of  an  elementary  character.     Text   and  other  reference 
books  which  pupils  enjoy  when  reading,  and  which  they  "can  under- 
stand," are  at  a  premium  so  long  as  these  characteristics  are  not  gained 
at  the  expense  of  scientific  and  pedagogical  worth. 

2.  Many  publications  of  the  United  States  Government  are  available 
free  or  at  a  nominal  price.     It  is  usually  best  to  order  these  through  the 
Congressman  of  one's  home  district,  especially  if  several  copies  of  any 
one  publication  are  desired.     Before  ordering,  however,  application 
should  be  made  to  the  Department  concerned  for  a  List  of  Publications 
suited  for  use  by  teachers  in  public  schools.    Lists  of  Farmers  Bulletins , 

1  In  providing  a  library  of  reference  books  for  use  in  General  Science  much 
disappointment  and  waste  will  be  avoided  by  ordering  so  far  as  possible 
only  books  with  whose  contents  in  a  general  way  at  least  the  teacher  has  be- 
come well  acquainted.  Printed  lists  of  books  secured  from  different  sources 
are  no  exception  to  this  rule  however  helpful  these  lists  may  be  in  narrowing 
one's  choices  for  examination. 


APPENDIX  373 

and  of  various  other  publications  of  great  value  in  teaching  General 
Science,  may  be  had  on  application  to  the  Division  of  Publications, 
Department  of  Agriculture,  Washington,  D.  C. 
3.  These  books  have  been  found  helpful: 

Bailey   (Mac.)1  Sanitary   and   Applied   Chemistry, 

Revised $1.50 

Bigelow  (Mac.)  Applied  Biology.  '. i  .40 

Comstock  (Com.)  Handbook  of  Nature 3-65 

Coulter  &  Patterson  (Ap.)     Practical  Nature  Study i  .40 

Eldridge  &  Briscoe  (Long.)  First  Aid  in  Laboratory  and  Work- 
shop    0.35 

Harrington  (Ap.)  About  the  Weather o. 70 

Parloa.  (Cent.)  Home  Economics i .  50 

Price  (Wi.)  Handbook  on  Sanitation i .  50 

Snyder  (Mac.)  Chemistry  of  Plant  and  Animal  Life, 

Revised i .  50 

Walters  (Heath)  .         Principles  of  Health  Control i .  60 

Weed  (Am.)  Chemistry  in  the  Home i .  20 

Wilson  &  Warburton( Webb) Field  Crops i .  50 

1  Publishers  of  books  as  listed  above  are:  (Mac.)  Macmillan  Company, 
New  York;  (Com.)  Comstock  Publishing  Company,  Ithaca,  N.  Y.;  (Ap.) 
Appleton  &  Co.,  New  York;  (Long.)  Longmans,  Green  &  Co.,  New  York; 
(Cent.)  Century  Company,  New  York;  (Wi.)  Wiley  &  Sons,  New  York; 
(Heath)  D.  C.  Heath  &  Co.,  Boston;  (Am.)  American  Book  Co.,  New  York; 
(Webb)  Webb  Publishing  Co.,  St.  Paul,  Minn. 


INDEX 


Absolute  temperature,  142,  146 
Absorption,  98 
Accidents,  233-239 

by  automobiles,  239 

liability  for,  237-238 
Acids   (bases,  salts),   180-183,   190- 
191 

definitions,  182-183 

formulae  for,  181 
Adenoids,  6 
Adulterations,  48 
Agriculture,    courses    in,    303,    316, 

317,  322,  332 
Air,  as  respired,  19-23 

compressed,  56,  120-122 

constituents  of,  23,  112 

in  soils,  251 

liquid  air,  116-118 

properties  of,  110-113 

weight  of,  112 
Air-brakes,  122-123 
Air  drills,  122-123 
Alcohol,  72-76,  78,  212,  238 

effect  on  nerve  centres,  76,  79- 

80,  238 

Alkali,  178,  189,  191 
Aluminum,  188-189 
Ammonia,  uses  of,  116,  118,  177 
Amusements,  68 
Anaesthetics,  78 
Antiseptics,  39 
Antitoxins,  37,  41,  60 
Apple  raising,  319-325 


Asbestos,  145 
Atmosphere,  110-131 

currents  in,  113,  123-131 
density  of,  in,  123 
depth  of,  in,  113 
Atmospheric  moisture,  effect  on  heat 

from  sun,  112 
in  relation  to  health,   20,   113, 

135-136 

Atmospheric  pressure,  114-132 
applications  of,  119-123 
currents  due  to,  123-126 
effects  on  persons  of  changes  in, 

115,  122 

measurement  of,  114 
relation  to  altitude,  115 
to  density,  118,  126-127 
to  wind  velocity,  114 
Atoms,  173 


Bacteria,  36-45,  i?5,  251,  324 
nitrogen-fixing,  44,  254,  313 

Balanced  diet,  209,  213,  219-224 

Balloons,  115 

Barometer,  114-115,  118,  131 

Bathing,  28 

Batteries  (cells),  170,  184,  187,  189 
storage,  187 

Birds,  275-280,  297 

bills,  and  feathers,  276-277 
migrations,  277-278 
usefulness  of,  278-279 


375 


376 


INDEX 


Blood,  circulation  of,  34 

pressure,  34 
Bluing,  laundry,  178 
Board  of  Health,  43 
Bodily  wastes,  7,  174 
Body,  human,  as  a  machine,  68,  72- 

73 

Boiling,  86-87 
Brain,  9,  65-66,  72 
Bread,  232,  325 
Breathing,  5-6,  19-25 

artificial,  23-24 

effects  on  digestion,  22 
Burns,  treatment  of,  235-236 
Business  success,  252-253,  293-295, 

298 
Butter,  and  butter  making,  342 

substitutes  for  butter,  272 


Caissons,  120 
Calendar,  353,  362 
Calorie,  95 
Capillarity,  249 
Carbohydrates,  27,  226-231 
Carbon  dioxide,  16,  18-19,  23,  190- 
191,  194-195,  268 

monoxide,  17,  201 
Casein,  301 
Catarrh,  6 

Caves  (caverns),  194 
Cells  in  living  bodies,  31,  64-65,  68, 
71-72,  175 

effect  of  heat  on,  27 
Cellulose,  226-228,  231,  268,  273 
Cement  and  concrete,  62-63,  Z92 
Character,  traits  of,  8,  243,  252,  293- 

295 

Chemical  changes,  173-179,  202 
agencies  in,  174-176 
by  electricity,  184-190 
equations  for,  179,  182,  184,  191 
factors  (and  products)  in,  182 
ionization  in,  181-182 


Chemical  changes  and  radicals,  182 

valency  in,  183-184 
Chemical  elements  and  compounds 

173-174,  197 
Chemical    formulae,    179,    181-184, 

191,  227 

Chest  walls,  21-22 
Chlorine,  uses  of,  175-176 
Chlorophyll,  226,  314 

chloroplasts,  226-227,  268 
Cisterns,  54-55 

Citizenship,  duties  of,  47,  245-246 
Clay,  198,  247-248 
Cleaning,  177-179 

dry  cleaning  of  clothing,  177 
Climate,  134-13? 

in  relation  to  civilization,  135 

in  relation  to  latent  heat,  96 
Clothing,  28-29,  209,  213,  272 
Clouds,  90,  94,  138-140 
Coal    (and   solar   energy),    196-199, 

215-217 

Codling  moth,  321-322 
Coefficient  of  expansion,  141-142 
Colds,  5,  28-29,  77 
Color,  342-348 

in  plumage  of  birds,  276 

selective  absorption  in,  343-344 
Combustion,  16-18 
Compressed  air,  119-122 
Condensation,  90-96 

heat  from,  95-96 
Congestion,  n,  28,  34,  65 
Conservation,  of  forests,  254-259 

of  soils,  103-105,  255 

of  well-being,  14,  210-213 
Constipation,  7,  22 
Consumers,  281-283 
Corn,  312-317 

climate  for,  313-314 

flowers  of,  315 

products  from,  316 

value  of  crop,  313,  31 7 
Correlation  of  forces,  346 


INDEX 


377 


Cost  of  living,  209-213,  256 
Cotton,  271-272 
Cows,  310-311 
Crop  rotation,  313 
Crystallization,  92 
"Cures"  for  ailments,  77 
Cyclones,  130-131 

D 

Dairying,  309-310 

Days  (and  nights),  148-149,  350-35  r, 
354,  361-362 

lengths  of,  354 

place  of  beginning,  361 

subdivisions  of,  362 
Density  of  bodies,  153,  357~358 

of  water  and  ice,  88,  141 
Diaphragm,  21-22 
Diffusion,  98-100 
Digestion,   6-7,    174,    219-221,   225, 

228 

Diphtheria,  39,  41 
Disease,  31-33,  36-45,  49,  54,  58-61, 

308,  311 

Disinfection,  43~45>  T76,  208,  235 
Dissipation,  71,  73,  80 
Distillation,  93 

natural,  94,  106 
Diurnal  circles,     148-149,     350-351, 

354,  356,  358 
Drowning,  23-24 
Drugs,  habit-forming,  75-80,  82 
Dwellings,  206-209,  218 
Dynamo,  168-172 


Earth,  the,  157,  193,  349-3 54 
Easter,  359 
Eclipses,  337-338 
Economic  conditions,  281-296,  327 
Education,  17,80-81,  210-212,  257, 
284,  293-294,  298,  349 


Efficiency,  31-32,  65-69,  72-75,  83, 
163,  167,  207,  211-213 

Eggs,  279,  299-303 
candling  of,  301 
preservation  of,  301-303 

Elasticity  (and  plasticity),  155 

Electric  lights,  218-219 

Electricity,  168-172,  184-190 

Electrolysis,  184-190 

Electromagnets,  168-172 

Electro-plating,  170,  185-186,  190 

Embryo,  302,  315 

Emergencies,  233-239 

Emetic,  234 

Emulsion,  177,  179,  310 

Energy,    160-163 

electrical,  1 68,  172,  190,  218 
molecular  (and  heat),  143,  147, 

161,  218 

of  ether  motion,  346-347 
of  the  human  body,    26-27,    29, 

31,  40,  67,  134 
solar,  161,  217 

in  relation  to  plants,  268,  274 
transformation  of,  160-161 
transmission  of,  160-163 

Enzymes,  174-175,  231 

Equilibrium,  165,  167 

Erosion,  103-108,  333 

Ether  medium,   144,   162-163,   172, 

218,  344-348 

absorption  of  motion  of,  147, 162 
wave  frequency  in,  162 

Evaporation,  86 

Evolution,  plants  and  animals,  302, 
305 

Exercise,  physical,  31,  36,  65-69,  72^ 

J75,  241 

Exercises  (see  Questions). 
Expansion    (see    Volumes   of   bodies 

coefficient  of,  141-142 
Eyes,  and  their  care,  10-15 

parts  of,  lo-n 
Eye-strain,  12-15 


378 


INDEX 


Faraday,  168 

Feathers,  276,  297 

Ferments,      and     fermentation,    6, 

i7S 

Fireless  cooker,  145 
Fires;  235-236,  239,  254-256 
Flame,  17-18,  235-236 
Flies,  57-60 
Flowers,  265-266,  315 
Food  inspection,  47-49,  51 
Foods,  classes  of,  27,  222-224 

quantity  needed,  219-220 
Food  stuffs,  45-48,  209,  220 

adulteration  of,  48,  226 

composition,  table  of,  225 
Forces,  151,  155,  157,  160,  163 
Forests,  254-258 
Friction,  154 
Frost,  92,  94 
Fruit,  262,  267 
Fuel,  214-217 
Fungi,  322-325 
Fusion,  heat  of,  95-96 


Garbage,  61 
Garden,  241-246 
Gases,  86,  98-99 

liquefaction  of,  116-118 

pressure  of,  117-118 

temperature  due  to  compression 
and  expansion  of,  90,  117- 
118,  125,  138 
Gasoline,  177,  235 
Gluten,  300,  327-328 
Gravity,  and  gravitation,   155-158, 

338 

Growth,  64,  71,  83,  302,  315-316 
Gypsum,  195 


II 


Habit  formation,  74-76,  80-84,  219, 

295 

Hand,  structure  and  uses,  2-3 
Headache  powders,  77 
Health,  i,  29,  31-36,  42-43,  49,  5$, 

61-69,  72-74,  208-209,  219- 

221,   223-224,  237,  241,  293 

in  relation  to  weather,  113,  133- 

137 

Heat,  116-117,  I43-I47 
and  electricity,  161,  218 
as  molecular  energy,  143-144, 161 
conduction  and   convection  of, 

I43-I4S 
liberated    by    condensation    or 

compression,  95, 117 
measurement  of,  94-95 
of  solution,  99 
of  vaporization,  95-96 
radiation  of,  144-145,  147 
reflection  of,  149 
solar  heating,  112,  149,  35i~352, 

367 

specific  heat,  87 
Heat  equator,  131 
Heavens,  the,  364-369 
"Highs"  and  "lows,"  129-131,  137- 

140 
direction   of   their   movements, 

129-131,  138-140 
Homes  and  their  surroundings,  206, 

214-215,  245-246,  283 
heating  and  lighting,   214-215, 

218-219 
rooms    and    their    furnishings, 

206-208 

Horizon,  147-149,  349~35* 
Horse,  304-307 
Humidity,  20,  93-94,  136-137 
Hygiene,  i,  25,  32,  35-36,  42-43,  65- 

69,  72-79 
Hypothesis,  98,  101 


INDEX 


379 


Ice,  50,  116 

density  of,  88 
Images  by  reflection,  338-342 

how  located,  340 
Immune,  36-37 
Incandescence,  18,  217-218 
Industrial  life,  281^-290 
Industries,   chemical,   188-192,   195, 
199-203 

iron,  197-204 

petroleum,  284-287 

relation  to  coal  supply,  196-199, 

216 

Inertia,  154 

Infection,  36-54,  61,  208,  236 
Initiative,  2  43 
Insects,  57-62,  278 
Instinct,  277-278 
Insurance,  235,  239 
Intemperance,  66,  69 
Ions,  and  ionization,    181-183,    l86> 

190 
Iron  (and  steel),  197-204 

cast  iron,  92,  201-202 

galvanized,  203 

pig  iron,  201,  204 

properties  of,  201-202 

tempering  of  (as  steel),  203-204 

uses  of,  196-197,  202-204 
Irrigation,  105,  108,  244,  247 

K 

Kerosene,  17,  235,  286 
Knowledge,  83-84,  210 


Labor,  281-284,  288-289,  292-295 

on  farms,  327-328 
Laws,  of  correlation  of  forces,  1 70 

of  definite  proportions,  16 


Laws,  of  gravitation,  155-156 

of  life,  68 

of  machines,  167 

of  science,  98 

of  "survival  of  the  fittest,"  265, 
279 

of  weather,  137 
Leaves,  262,  264,  267,  270 
Levers,  163-167 
Life,  64-68,  71,  78,  356 
Light,  diffusion  of,  179,  341 

in  relation  to  heat,  217-218,  346 

phenomena  of,  336-348 

reflection  of,  339~34i,  344 

refraction  of,  341,  343 

velocity  of,  337 
Lime,  in  water,  178-180 

for  builder's  uses,  191-192,  195 
Liquids,  86 
Literature,    relation   of    to   science, 

in,  242,  258,  364 
Litmus,  180-182 
Lumber,  255-256 
Lungs,  and  their  capacity,  22,  25 
Lymph,  71-72 

M 

Machines,    163-164,    166-167,    169- 
170,  196,  239,  284-285,  288, 

295 

for  farm  uses,  310,  327-331 

the  human  body  as  a  machine, 

26,  29,  66 

Magnetism,  170-172 
Malaria,  38,  6 1 
Mammals,  305-306 
Manhood,  81-83 
Marble,  193-194 
Mass,  152,  155-156 
Matches,  friction,  176 
Matter,  151-158 

indestructibility  of,  152 

living  matter,  151-152 

properties  of,  152-155 


38o 


INDEX 


Medicines,  purpose  of,  33-36,  65,  78 
Mercury,  boiling  and  freezing  tem- 
peratures, 142 

coefficient  of  expansion,  141 

properties  of,  141-142,   146-147 
Metabolism,  174-175 
Metals,  188-189,  194-205 

importance  of,  196-197 
Milk  supply,  226,  308-311 

pasteurization  of,  309 
Mind,  8-9,  65-66 
Molecules,  85-86,  173-174,  181 
Moment,  165-167 
Momentum,  166-167 
Moon,  157,  353,  355-358 

number    of    moons    for    other 
planets,  358 

phases  of,  355,  358 

physical  characteristics,  357-358 
Mosquitoes,  39-40,  6c-6i 
Mouth,  4-6,  8-9 

connected  parts,  4-5,  9 
Narcotics,  73-79 
Natural  resources,  103-105,  107,  218, 

254-256,  284-287 
Nerves,  2-3,  5,  8-9,  31,  33,  79 

nerve  shock,  236,  239 
Nitrogen,  112-113,  257 


Obliquity  of  solar  rays,  147-149,  351- 

'352 

Oils,  231,  272-273 
Ores  of  the  metals,  194-201 
Osmosis,  99-101 

osmotic  pressure,  100 
Oxidation,  16-18 
Oxygen,  16-18,  175,  226 

liquid  oxygen,  117-118 


Pain,  n,  33,  35 

Paint,  203,  208,  272-273 

Paper,  273-274 


Parasites,  40 

Pasteur,  36,  39 

Patent  medicines,  76-77,  79 

Pendulum,  359,  362 

Perspiration,  27-29 

Petroleum,  284-288 

Phenomena,  152 

Planets,  337~338,  353,  367-369 

Plant  growth,  conditions  for,  243, 
247-251,  253 

Plants,  studies  of,  263-274 
flowers,  265-266 
leaves,  263-265,  267-270 
propagation  of,  266-267 
roots,  243-244,  248-249,  263,  267 
seeds,  265-266 

usefulness   of   plants,    255-259, 
263-265,  268-274 

Play,  69-71 

Pollen,  265-266 

Potato,  229 

Poultry,  297-303 

structure    of    bodies    of    fowls, 
297-298 

Poverty,  73,  212-213,  290-291 

Preservatives,  47-48,  51,  307 

Producers,  281-283 

Proteins,  27,  220,  222-225,  231,  299- 

300,  328 
test  for,  301 

Protoplasm,  64,  71,  79,  222,  226 

Protosynthesis,  228  ^ 

Protozoa,  36-38,  40 

Ptomaines,  41,  47 

Public  health,  47-51 

Pulleys,  164 

Pumps,  122 

Pure  foods,  48,  51 

Q 

Quarantine,  43,  45 

Questions,  lists  of,  15,  30,  51-52,  63- 
64,  84, 97, 101, 108-109, 123, 
131-132,  140,  150,  158-159, 


INDEX 


Questions,  lists  of  163,  168,  172, 180, 
213-214,  232-233,  239-240, 
247,  254,  259,  275,  280,  289- 
290,  303-304,  307,  312,  3i7- 
318,329-332,  348,  354-355 


Rainfall,  90-92,  94,  136,  138-139 

Rats,  61-63 

Recreation,  68-72 

Refrigeration,  118,  145 

Resistance,  154,  164,  167 

Respiration,  19,  24,  in 

Rest,  n,  66-72 

Revolution  of  earth,  148,  154,  157, 

351-355 

"leap  year,"  353 
lengths  of  years,  353 
velocity  of,  353 
Right  living,  65-84,  207-208,  211- 

213 
Rocks,  334-335 

limestone   (see  Gypsum),    192- 

196,  202 
sandstone,  194 
stratification  of,  192-193 
Roots,  243-244,  314 
Rotation  of  earth,  128,  131,  349-351 
rate  of,  350-351 


"Safety  first,"  238-239 

Saliva,  6 

Sand,  247-248 

Sanitation,  46-51 

Schoolrooms,   conditions  in,    13-14, 

20-21,  23,  41 
Schools,  purposes  of,  26,  42,  49,  51, 

68,  80-82,  84,  207,  2 1 1-2 1 2, 

252,  257,  292-296 
Science,  achievements  of,  284,  289, 

295 


Seasons,  351-354 
Seeds,  265-267 
Serums,  37,  41,  45 
Sewage,  56 

Shadows,  336-33?,  357 
Sickness,  32-33,  35,  42,  57,  65,  74, 
175 

by  inheritance,  32 

treatment  of,  33 
Silos,  316 

Sleep,  19,  25,  32,  66-68,  72 
Soap,  177-178,  19 

Social  welfare,  41-43,  46-49,  61-62, 
69-71,  74-75,  287-288,  290- 

295 

Soda,  manufacture  of,  190-191,  195 

Soils,  247-254,  332-335 

classes  of,  247-248,  251,  332-333 
fertility  of,  251,  313 
humus  in,  251,  333 
origin  of,  333~335 
sorting  of  by  water,  333 
temperature  when  water-soaked, 

96 

tillage  of,  243,  246,  248-254 
water  content  of,  248-249 

Solar  heating,  and  obliquity  of  rays, 
142-149 

Solar  spectrum,  342-347 

Solids,  86,  98 

Solutions,  88-90,  98-99,  101 

Specific  heat,  89,  146-147 

Spectrum  analysis,  345-346 

Sports,  70 

Sprains,  3 

Sprays   and  spraying,  122,  321-323, 

325 

Standard  time,  359-363 
Starch,  222,  226  -229,  231,  317,  328 
Stars,  366,  368-369 
Sterilization,  45,  234,  236,  311 
Stimulants,  72-99 
Storage  batteries,  120,  187 
Strain  (and  stress),  154 


INDEX 


Streams,  103,  106 
Sublimation,  92 
Submarines,  119-120 
Sugar,  222,  224,  227-231 
Sun,  351-354,  367-369 

atmosphere  of,  337~338 
distance  of,  352-353 


Teeth,  8,  10,  277,  305-307 
Telegraphy,  wireless,  172 
Temperate  living,  67-70,  73-74 
Temperature,  86,  140-147 

boiling,  and  freezing,  86,  99,  146 

in  relation  to  volume,  140-141 

of  human  body,  27-29 
Tempering,  203-205 
Tenacity,  155 
Tendons,  2 

Theories,  as  to  light,  338-339,  344~ 
347 

in  astronomy,  337 

of  conduct,  293-295 

of  education,  294,  296-29; 

of  science,  71,     152,     160,     162, 

181-182,  186 
Thermometers,  140-142,  146-147 

clinical,  35 

Thermos  bottle,  117,  145 
Thrift,  134,  209-213,  235,  290-203 
Timekeeping,  359-363 

international  date  line,  361 

local  time,  359 

standard  time,  and  time  belts, 

360-363 

Tobacco,  74,  79,  211 
Tonsils,  5 
Tornado,  125-127 
Toxins,  40-41,  45 
Transpiration,  270,  314 
Transportation,  53,  85,  281-283 
Trees,  254-263 

planting,  and  uses  of,  256-259 

studies  of,  259-263 


Tuberculosis,  25,  39 
Typhoid,  37-38 

V 

Vaccination,  37-38 
Vaporization,  90-96 

heat  of,  94-96 
Varnish,  273 
Veins,  valves  in,  34 
Velocity,  157,  337,  350-351 
Ventilation,  20-21,  23-25,  122 
Volumes  of  bodies,  changes  in,  20,  88, 
93,  116-124,  141-142,  146- 


W 


Wage  earning,     283-284,     290-291, 

295 

Washing  powders,  178,  191 
Waste,  26,  29,  32,  35,  42,  49~5o,  61- 
62,  66-68,  74-75,  82,  103- 
105,  134,  160,  206,  212,  218, 
257,  279,  293     „ 
Water,  and  plant  growth,  269 
as  a  drink,  7,  49,  224 
carbonated,  88-89 
"hard"  water,  178-180 
in  the  breath,  23 
in  relation  to  health,  53-57 
peculiar  behavior  of,  141 
properties  of,  86-90 
purification  of,  53-57 
sources  of  infection,  50,  53-54, 

56 

supply  of,  53-57 
uses  of,  52-53,  56,  85 
Water    in    the    atmosphere,    93-94, 

123-126 
Weather,  133-140 

and  health,  113,  133-136 
due  to  highs  and  lows,  137-140 
forecasts  of,  137-139 
protection  from,  133 
Weight,  156 


INDEX  383 

Wells,  54  Winds,  constant  and  variable,  128- 
Wheat,  325-328  130 

food  value  of,  327-328  Wood  pulp,  273-274 

regions  where  grown,  325-328  Work,  160-163 
Winds,   94,    in,   113-114,   123-131,  Y 

137-139  Yellow  fever,  39-40 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
This  Jyfok  isLDUE.  on  the  last  date,  stamped  belojg. 


TO32    1969 
MAR  1     1969 

RECEIVED 

'7 '69  -8  A 

LOAN  DEPT 

LD  21-100l».12,'46(A2012si6)4120 


0 


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YC  22703 


387901 


Q i 

5? 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


